HAMILTON MODEL 121 AIR FORCE 24 HOUR CHRONOMETERS

The following account of these chronometers was put together from the original Hamilton records, internal memos, and copies of various letters to and from the companies involved.

Sometime in late 1941 or early 1942 (the exact date is unknown) the U.S. Army Air Force contacted the Hamilton Watch Company and requested that they supply the Army Air Force with chronometers to be used as a master time source.
The chronometers were to be configured with black 24 hour dials with white hands and white numerals and were to be mounted in individual chronometer boxes with gimbals, similar to the existing Model 21’s, with three individual chronometers mounted in a vibration free wood carrying case.
Contract number W535-AC-29502 was received and Hamilton spent most of 1942 working on the final specs and assembling the necessary parts. The original specifications called for the dial to be inscribed U.S. Army Air Corps and the 3 units carrying case identification plate to be inscribed as Master Time Source. In a letter dated July 25, 1942, the Material Division, Army Air Force, Wright Field, requested, without explanation, that the dial be changed to read U.S. Army Air Force and the carrying case identification plate be changed to read Chronometer Unit.

Hamilton designated the units to be Model # 121 starting with serial number 3E 001. As per the specifications the serial number was to be applied to the dial, the pillar plate, the barrel bridge, and the front of the gimbaled mounting box. The carrying case indentification plate was to be numbered starting with number 42-1.
Three each of the chronometers were to be placed in a carrying case with vibration damping mountings. Hamilton started work on the chronometers in late 1942, using the existing 14 Jewel Model 21’s and converting them to the 24 hour dial configuration.
These units were designated as Model 121, part number 42221, and using dial # 42236.
Hamilton outsourced some of the parts needed, most notably to the National Lock Co., Rockford, Ill, for the box hardware, the Lord Manufacturing Co, Erie, Penn., for the vibration suspension mountings, and to the Seth Thomas Clock Co., for the chronometer boxes and the 3 unit carrying case. The first 3 unit set was delivered to the Army Air Force at Wright Field, Dayton Ohio, on March 4, 1943. The original contract called for a total of 9 three unit sets, but the last three sets were cancelled on August 19, 1943, ( for reasons unknown), so only a total of 6 three unit sets were built.
The only 3 unit set known to have survived intact is serial number 42-3, holding chronometers number 3E 007, 3E 008 & 3E 009.

The enclosed 1943 memo indicates when the deliveries were made to the Army Air Force:


Contract……….. 1943 - Account with Model 121
W-535………… FINANCE OFFICER ( 3 ) - 85 si
AC-29502……… Wright Field 14 J Air Force
Purchase order.. Dayton, 0. Chronometers
# 42-20399-P….. Terms: 30 days net
…………………..
Invoice No…….. 3-4-7520…………1-—-Air-Force Chronometer Unit …………………$1,500.00
………………………..Model #121 Dial # 42236
…………………………………………….Delivered to
………………………………..Capt. Jno. C. Goodell
………………………………………….of Wright Field
………………………………….on train enroute from
…………………………Phila. to Dayton, Train #31
……………………………………….At Lancaster Pa,
……………………………………(Unit No. A.F. 42-1)
……………………consisting of (3 # 85 si. Models
…………………………# 3E 001 - 3E 002 - 3E 003

Invoice No…….. 3/10-7651………….1—Air-Force Chronometer Unit …………………$1,500.00
……………………………………………Model # 121
……………………………………Delvd personally to
……………………………………Lt. P. W. Johnston
…………………………………………at Wright Field
………………………………by Messrs M.F. Manby
………………………………………..& L.F, Halligan
……………………………………..(Unit No.A.F.42-2)
…………………..Serial # 3E 004 - 3E 005 - 3E 006

Invoice No……... 4/8-8728…………1-—Air-Force Chronometer Unit $1,500.00
…………………………………………….Model #121
………………………………….(Unit No. A.F. 42-3)
……….………..Serial Nos. 3E 007 3E 008 3E 009

…………………………………Delvd by Mr. Halligan
…………………………………to, Lt. P.W. Johnston, ……………………………………………Wright Field


Invoice No…… 5/19-1975………….1---Air-Force Chronometer Unit $1,500.00
………………….. Model # 121………………. 42236……………
…………………. ………………………………..…(Unit No. A.F. 42-4)
…………………. ……………..…Serial Nos. - 3E 010 3E 011 3E 012
…………………..
…………………..
………………….. ………………………………Delvd by Mr. Halligan to
………………….. ……………………………………….P.W.Johnston at
………………….. …………………………………………….Wright Field
…………………..
Invoice No…… 6/17-10730………1---Alr-Force Chronometer Unit $1,500.00
…………………. ………….Model #121………… 42236 ………..
…………………. ………………………….……….(Unit No. A.F. 42-5)
…………………. ………………….Serial Nos. 3E 013 3E 014 3E 015
………………….
………………….
………………….. …………………………..Delvd to Lt. P.W. Johnston
…………………. …………………………………………at Wrlght Field
………………….. ………………………………………by Mr. Halligan
………………….
………………….
………………….
………………….
………………….
………………….
………………….
Contract………. ……………. l——AIR-Force Chronometer Unit….. …….. ……..Model 121
W-535………… …………. Model #l21………………………... …………..(3)-85 size-14
AC-29502…….. ……………………………(Unit No. A.F. 42-6) …………. AIR-FORCE
Purchase Order …………..Serial Nos. 3E 016 3E 017 3E 018 ……CHRONOMETER
#42-20399-P…. ………………___UNIT
………Terms:Net 30 day

…..Invoice #….. …………………………Delvd by Mr. Halligan …………$ 1500.00
7/25-10959…… ………………………….to Lt. P.W. Johnston …………………………….
…………………………………at Wright Field …………………………….
…………………………….
…………………………….
…………………………….
…………………………….
………………… Model # 121 is composed of 3 # 85 si Chrono …………………………….
…………………. Each Chrono consists of the following; …………………………….
…………………. Movt - Model 121 - Part 42221 …………………………….
…………………. Case and Gimbal Assembly - Part- 42100 …………………………….
…………………. Case Suspension - Part 42235 …………………………….
…………………. Box Mounting - Part 42222 …………………………….
…………………. Dial - # 42236 …………………………….
…………………. Inspected and approved by Army Air Force Resident Inspector, …………………………….
…………………. Movement - 85 size -. l4jewel - Model 121 - Part 42243 …………………………….
…………………. Hand - Hour - 42237 …………………………….
…………………. Min - 42238 …………………………….
…………………. Sec. - 42239 …………………………….
…………………. Wind Indicator - 42243 …………………………….
…………………. Serial number of movement assigned by Hamilton is to be …………………………….
…………………. engraved on pillar plate, barrel bridge, .face of dial ……………………………
…………………. and front of mounting box. …………………………….
…………………. Serial number of Chronometer Unit assigned by A.A.F. to …………………………….
…………………. be engraved on name plate fastened to front of Susoension …………………………….
…………………. Case - Serial numbers from A.F. 42-1 to A.F. 42-.9 inclusive. …………………………….
…………………. Inspection - At Contractor's Plant. …………………………….



After the Army Air Force cancelled the chronometer order Hamilton continued to build the 24 hour version of the Model 21, building a total of 42 units, although no information exists for 3E 041 and 3E 042.

Only units 3E 001 thru 3E 018 ( and possibly units 3E 022 & 3E 023) have the Army Air Force dial. The remaining 22 units have a black 24 hour dial, part number 42253, simply marked Hamilton Watch Co. These units, for the most part, were sold to three west coast instrument companies: Northwest Instrument, Seattle Wa, and the George E.Butler Co. & The Louis Weule Co., both from San Francisco, Ca.



.SERIAL #.. .COMPLETED …DATE SOLD… …ORDER #… ………..PURCHASER………….
3E 001……. 3/4/1943……... 3/4/1943………. 64-7520…….. U.S. ARMY AIR FORCE
3E 002……. 3/4/1943……… 3/4/1943………. 64/7520…….. U.S. ARMY AIR FORCE
3E 003……. 3/4/1943……… 3/4/1943………. 64/7520…….. U.S. ARMY AIR FORCE

3E 004……. 3/10/1943…….. 3/10/1943……… 64-7657…….. U.S. ARMY AIR FORCE
3E 005……. 3/10/1943….... 3/10/1943……… 64-7657…….. U.S. ARMY AIR FORCE
3E 006……. 3/10/1943……. 3/10/1943……… 64-7657…….. U.S. ARMY AIR FORCE

3E 007……. 4/8/1943…….. 4/8/1943………. 64-8728…….. U.S. ARMY AIR FORCE
3E 008……. 4/8/1943…….. 4/8/1943………. 64-8728…….. U.S. ARMY AIR FORCE
3E 009……. 4/8/1943…….. 4/8/1943………. 64-8728…….. U.S. ARMY AIR FORCE

3E 010……. 5/19/1943…… 5/19/1943…….. 64-9775…….. U.S. ARMY AIR FORCE
3E 011……. 5/19/1943…… 5/19/1943…….. 64-9775…….. U.S. ARMY AIR FORCE
3E 012……. 5/19/1943…… 5/19/1943…….. 64-9775…….. U.S. ARMY AIR FORCE

3E 013……. 6/17/1943…… 6/17/1943…….. 64-10730……. U.S. ARMY AIR FORCE
3E 014……. 6/17/1943…… 6/17/1943…….. 64-10730……. U.S. ARMY AIR FORCE
3E 015……. 6/17/1943…… 6/17/1943…….. 64-10730……. U.S. ARMY AIR FORCE

3E 016……. 7/15/1943…… 7/15/1943…….. 64-10959……. U.S. ARMY AIR FORCE
3E 017……. 7/15/1943…… 7/15/1943…….. 64-10959……. U.S. ARMY AIR FORCE
3E 018……. 7/15/1943…… 7/15/1943…….. 64-10959……. U.S. ARMY AIR FORCE

3E 019……. 2/8/1946……. 3/13/1947…….. 38024………. GEORGE E. BUTLER CO.
3E 020……. 7/13/1944…… 7/23/1946…….. 28429………. GRAVES STEWWER CO.
3E 021……. 6/27/1946…… 6/27/1946…….. 27998………. GEORGE E. BUTLER CO.
3E 022……. 10/9/1944……. 10/9/1944……… 64-17354……. U.S. ARMY AIR FORCE
3E 023……. 10/9/1944……. 10/9/1944……… 64-17354……. U.S. ARMY AIR FORCE
3E 024……. 11/17/1944…… 11/17/1944……. 17828………. NORTHWEST INSTRUMENT
3E 025……. 8/15/1944…… 8/15/1944……… 16691………. NORTHWEST INSTRUMENT
3E 026……. 11/2/1944…….. 11/2/1944……… 17684………. NORTHWEST INSTRUMENT
3E 027……. 11/17/1944…… 11/17/1944…… 17828………. NORTHWEST INSTRUMENT
3E 028……. 6/5/1946……. 6/5/1946……… 25765………. LOUIS WEULE CO.
3E 029……. 7/2/1945…….
3E 030……. 6/21/1946…… 6/21/1946…….. 27646………. GEORGE E. BUTLER CO.
3E 031……. 7/25/1946…… 7/25/1946…….. 28545………. LOUIS WEULE CO.
3E 032……. 7/25/1946…… 7/25/1946…….. 28545………. LOUIS WEULE CO.
3E 033……. 2/5/1946……. 8/7/1946……… 28659………. GEORGE E. BUTLER CO.
3E 034……. 8/30/1946…… 4/15/1947…….. 39484………. GEORGE E. BUTLER CO.
3E 035……. 9/17/1946…… 9/17/1946……. 30083………. GEORGE E. BUTLER CO.
3E 036……. 9/17/1946…… 9/17/1946……. 30083………. GEORGE E. BUTLER CO.
3E 037……. 9/25/1946…… 9/25/1946……. 30227………. GEORGE E. BUTLER CO.
3E 038……. 1/9/1947……… 1/9/1947………. 36596………. GEORGE E. BUTLER CO.
3E 039……. 2/19/1946…… 2/19/1946…….. 23356………. KARL PLEPLA
3E 040……. 1/3/1947……… 1/3/1947………. 31244………. LOUIS WEULE CO.
3E 041…….
3E 042…….

The following notes include what is currently known about the surviving units.
In the status column a ( pc ) indicates the chronometer is in a private collection.
( u ) indicates current status in unknown.

….SERIAL #…. ………………………NOTES……………………………….. ..STATUS..
3E 001…….. …………………………………………………………………… …..U…..
3E 002…….. ……………………………………………………………………. …..U…..
3E 003…….. …….CONV. TO 12 HOUR DIAL BY HAM.6/2/54……….. .…..P C…..
………( PROBABLY DUE TO LACK OF PARTS)……….
3E 004…….. …………………………………………………………………… …..U…..
3E 005…….. …………………………………………………………………… …..U…..
3E 006…….. …………………………………………………………………… …..P C…..
……………………………………………………………………
3E 007…….. …………ONLY COMPLETE 3 BOX SET………………... …..P C…..
3E 008…….. ……KNOWN TO………. …..P C…..
3E 009…….. …….….HAVE SURVIVED………. …..P C…..
……………………………………………………………………
3E 010…….. ……………….DIAL MARKED 3E 006………. …..P C…..
3E 011…….. …………………………………………………………………… …..U…..
3E 012…….. …………………………………………………………………… …..U…..
……………………………………………………………………
3E 013…….. …………………………………………………………………… …..P C….
3E 014…….. …………………………………………………………………… …..U…..
3E 015…….. …………………………………………………………………… …..U…..
……………………………………………………………………
3E 016…….. …………DIAL MARKED 16 MOVEMENT # 12485………. …..PC…..
3E 017…….. …………………………………………………………………… …..U…..
3E 018…….. …………………………………………………………………… …..U…..
……………………………………………………………………
3E 019…….. …………………………………………………………………… …..U…..
3E 020…….. ……..MEMO INDICATES UNIT WAS DONATED………. …..U…..
3E 021…….. …………………………………………………………………… …..U…..
3E 022…….. …….3E 022 & 3E 023 MOST LIKELY SOLD TO………. …..U…..
3E 023…….. …….AIR FORCE AS SPARES / SPARE PARTS………. …..U…..
3E 024…….. …………………………………………………………………… …..U…..
3E 025…….. …………………………………………………………………… …..U…..
3E 026…….. …………………………………………………………………… …..U…..
3E 027…….. ………………………………………………………………….. …..U…..
3E 028…….. …………………………………………………………………… …..U…..
3E 029…….. MARKED G.C.T. ON DIAL & WAS BREAK CIRCUIT…… …..P C…..
3E 030…….. …………………………………………………………………… …..U…..
3E 031…….. …………………………………………………………………… …..U…..
3E 032…….. …….MARKED PROPERTY US ARMY ON DIAL………. …..P C…..
3E 033…….. …………………………………………………………………… …..U…..
3E 034…….. …………………………………………………………………… …..U…..
3E 035…….. …………………………………………………………………… …..U…..
3E 036…….. …………………………………………………………………… …..U…..
3E 037…….. …………………………………………………………………… …..U…..
3E 038…….. …………………………………………………………………… …..U…..
3E 039…….. …………………………………………………………………… …..U…..
3E 040…….. …………………………………………………………………… …..U…..
3E 041…….. …………NO INFORMATION ON 3E 041 & 3E 042………..
3E 042…….. ……………….IS CURRENTLY AVAILABLE………..

Hamilton also made a 2nd run of 24 hour movements. These movements are marked 2E on the dial and movement and are in the narrow serial number range of 2E 12215 thru 2E 12240.
Its not known if all 25 units were built because records only exist for the following:
The two units indicated might currently be at the NAWCC Museum
2E 12215-PC
2E 12218
2E 12227
2E 12229-box only at the NAWCC Museum ??
2E 12230
2E 12232
2E 12233-NAWCC Museum movement & dial marked 2E12233 box marked 2E12229 ?
2E 12238
2E 12239
2E12240
Any information as to the whereabouts of any of the unknown 3E or 2E 24 hour units would be greatly appreciated.

Regards
Fred Hougham

AF6

AF3

AF2

AF10

AF11

AF7

Hi Fred,

Thank you for your well researched and informative post. With any luck, someone will post the whereabouts of a few of the unknowns.

BTW: It seems to me that the information you have assembled would make an interesting article for the NAWCC Bulletin.

Best regards,

Greg

Fred,

What a nice collection. Thanks for sharing them with us.

Matt

Wow

Fred where did you find these?

Scott,
Sorry about the delay in answering your question. This unit was purchased by my father in Oklahoma in 1992 from an estate along with numerous other chronometers. The unit was displayed at numerous regional and national NAWCC shows over the 9 years he had it in his collection. My father decided in 2000 to start reducing his military collection ( due to health and age) and the unit was sold to a private collector in 2001. Luckily I ended up with copies of the original Hamilton records and the pictures I took when the unit was in his possession, so I was able to put together the information posted.
Regards
Fred

Fred,
After reviewing your list I have this information to add. I have 24 hour chrono 3E014 with movement 2E12483. I found it interesting that your list shows 3E016 with movement 2E12485. It looks like these dials were fitted with movements in numerical order and dial 3E015 most likely has movement 2E12484. My dial is marked on the left side "Hamilton U.S.A." and on the right side in a milled oval area "Model M-21". My dial is different from the ones you show here in that my dial has the early style double ring seconds circle. I understand that these dials were the first run made for the original 3E machines but were rejected by the Army Air Force and replaced by the type you show. It is my understanding that these rejected dials were later placed on the second series machines with 2E movements.
Thanks for your information on these interesting machines.
Jim Dyson

Hi Jim,
Dad said to tell you " Hello"
You could very well be correct about the dials. In a letter dated 1/23/43 from E.W DREASCHER , (watch design supervisor) to M.F. MANBY, (chief engineer), states as follows:
"On finished drawing # 42236-2-01, for the U.S. ARMY AIR FORCE CHRONOMETER DIAL, the inside circle on the seconds track has been removed in accordance with the way the dials were actually made. These changes have been made to bring the drawing up to date in the event that further orders for this part may materlize."
I have no records to indicate when the dials were actually produced and then rejected by the Air Force. I assume your dials seconds bit area is similar to below.
This dial, along with a complete 24 hour gear set, was included with the records I have. The dial came from Bob Ravel, and was given to dad because it matched one of the boxed chronometers. I understand there were about 6 of these dial sets in Bob Ravels Hamilton materials. I have no records to indicate how the dials found their way onto the chronometers, or when they were installed.
Regards
Fred (jr.)

Fred,
Please give my regards to your father. He is one of the great collectors. Thanks for posting the picture of your dial 3E008. My dial is like it in all respects with the exception of the signature on the right, "U.S. Army Air Forces". On my dial this signature was milled off and remarked "Model M-21". I will post a photo of my dial soon. Larry Crutsinger, has the factory timing card for my machine, dial/movement 3E014/2E12483, which indicates that this machine did come from the factory assembled as it is today. The milled dial is strong evidence that it was material that was on hand but needed to have the U.S. Army Air Force signature removed as it was not sold to the the U.S. Army Air Force. Hopefully I will be able to discover who the orignal buyer was with some addition research.
Jim Dyson

Fred,
After visiting with Larry Crutsinger I have this additional information on 24 hour dial Hamilton 21 machines. As I stated before my 24 dial machine is numbered on the dial 3E014 with movement 2E12483. The Marine Chronometer Performance Test card that Larry has for this machine shows it was sold to Geotechnical Corporation on 9/8/1958 and was returned 2/3/1959 for additional testing. If anyone knows anything about Geotechnical Corp, I'd like to hear from you. The card states that this machine was fitted with 24 hour dial. Additionally Larry has has another second series machine with dial 3E011 and movement 2E12489. This makes three second series machines that I have seen including the one on your list 3E016/2E1485. My first thought, that these machines had dials and movement assembled in numerical order, is incorrect, but the movements are all from a very similar batch. All three of these 2E1248x movements have the later style straight line brushed finish on the movement plates instead of the earlier bar type damascene pattern. It is my understanding that the workman who did this type of work had retired by the late 50s. All three of these machines have US Army Air Force milled off and remarked Model M-21. Larry told me he has several unused 24 hour dials as your 3E008 signed US Army Air Force which indicates that not all of the rejected dials were used to make second series machines. Quite a few of these remained unused at the factory and were sold to Dr. Bob Ravel and subsequently to Larry Crutsinger. Larry and I plan to review the test cards and his unused dials and see if we can come up with additional information.
Jim Dyson
http://www.chelseaclockmuseum.com

Greetings,

For 3E017, we can change the line to read:

3E 017…….. …………………………………………………………………… ….PC…..

The following are some pictures of the chronometer.

The Serial on the movement:

Overall:

it doesn't get much nicer than that !!!!

Finer timepieces do not exist!

William