WWT Shows CLICK TO: Join and Support Internet Horology Club 185™ IHC185™ Forums

• Check Out Our... •
• TWO Book Offer! •
Go
New Topic
Find-Or-Search
Notify
Tools
Reply to Post
  
G.C.T. What is the meaning and why? "Click" to Login or Register 
posted
Hello all,

I have just aquiered my first Hamilton 4992B GCT contracted in 1943. I'm sure most of you have one so there is no better place to ask dumb questions. I know that it is thought that GCT stands for "Greenwich Civil Time" and that this was changed to GMT "Greenwich Mean Time" in 1952.
For what purpose would these initials be placed on the dial of such a watch? I know these watches were used primarily for navigational use by the Army Air Force so maybe there is a connection there with an abreviated purpose? Can anyone think of anything? I know the government would not have placed such an abreviation on tens of thousands of watches just because it looks nice. Is there any period documentation of this request by the US Government connecting this to Greenwich Civil Time?
I am sorry if this topic has come up before in one of your discussions. I do not want to kick a dead horse.
This watch makes number 2 in my WW2 Hamilton collection. I also have a Army Airforce Model 22 contracted to 1945. Next would be the infamous Model 23. Looks like I will have to remortgage...ha ha. Thank you all for any imput you may have. I respect all opinions.
 
Posts: 478 | Location: Southcoast Massachusetts | Registered: May 13, 2010
IHC Member 1291
Picture of Buster Beck
posted
Hi Michael,

I am here to confuse you more Eek
Greenwich Civil Time, not to be confused with "Grand Central Time", in traditional astronomical usage was " mean solar time" reckoned from midnight. Pre 1925 the U.K & the U.S. used "GMT"[except post 1924 GCT was used], until 1952.
For many years seamen & navigators have referred to GCT/GMT also as Z time Eek GMT is noted as GCT and lately to the universal community as Coordinated Universal Time[UTC] Now note this Wink The initials UTC do not fit Coordinated Universal Time Confused And its because the United Nations considers "french" as the international language, and UTC is how those 3 initials would appear in French Roll Eyes
Modernly speaking, civil time is generally standard time in a time zone at a fixed offset from GMT or UTC and possibly adjusted by daylight savings time, referenced by atomic clocks, adopted in 1972 Cool
Another interesting side note Roll Eyes In 1928 the International Astronomical Union introduced "universal time" for GMT but the two Nautical Almanac Offices for the U.K & the U.S. did not accept it until 1952 Frown
Hello~ Are we there Yet~ Are we Z time~ Still Confused Confused
Bottom Line; One thing you can be sure of wherever you are and by land, by sea, by air Roll Eyes
Whether its GMT/GCT/UTC/Z, time always relates to the time at 0 degrees Longitude[at the prime meridian] which the heart of lies in Greenwich, England..
Just 'er keep that watch wound in case the atoms collide or communication breaks down between nations, "we~we" , I mean "Oui~Oui" Wink Next Problem??? Big Grin Big Grin

Perhaps that will help to answer you're question Smile as during that specific time frame the U.S. used "GCT" Cool

regards,
bb
 
Posts: 6363 | Location: Texas in the USA | Registered: July 27, 2009
posted
Thanks Buster, that clears that up. M.
 
Posts: 478 | Location: Southcoast Massachusetts | Registered: May 13, 2010
IHC Life Member
posted
Some of my GCT watches...




Not all GCT watches are 24 hour watches...

Waltham USN GCT...











Elgin USN GCT...






I love white dialed military watches...




...and the odd rare prototype...

Hamilton Type A-9 prototype...










...as well as the truly unknown... at least to me...

Elgin Avion w/U.S. Army A.C. movement...



 
Posts: 101 | Location: San Antonio, Texas in the USA  | Registered: July 25, 2006
IHC Member 1291
Picture of Buster Beck
posted
James,

That's a very nice collection, and very impressive also Eek

Thank you for sharing it with us Smile

regards,
bb
 
Posts: 6363 | Location: Texas in the USA | Registered: July 27, 2009
IHC Life Member
posted
Thanks bb,

Really, my focus is on US issued military wrist watches. I think that part of my collection is way more impressive than my small amount of pocket watches.

Where exacty in Texas do you live? My home is in San Antonio but I am working overseas at the moment.

James
 
Posts: 101 | Location: San Antonio, Texas in the USA  | Registered: July 25, 2006
posted
James
It's not only impressive,it's fantastic.
Thanks for sharing, Hub.
 
Posts: 136 | Location: Warren, Oregon in the USA | Registered: May 28, 2008
Picture of Charles Grayson
posted
That is quite a collection, I like that "Elgin Avion" with the "Flight Hours" designation.

Very cool watches.

Charlie
 
Posts: 2 | Location: Northern Ohio in the USA | Registered: December 08, 2009
IHC Life Member
posted
Thanks guys. I mainly collect watches that I can wear. Not a single watch in my collection would I be afraid of wearing, even my rare Bulova USN protoype which I wore just yesterday. The day before that, I was wearing a RCAF Hamilton for half the day. You don't too many of those. Pocket watches are just not that practical compared to wrist watches. Having said that, I find myself every so often being attracted to the quality and uniqueness of some of these watches even though I seldom will carry one. I do have them on my desk from time to time and my 24hr Longines GCT permanantly sits in a glass dome on my desk so that I can always know witha quick glance the exact time back home. They are objects of beauty in my opinion, even though they were tools of war at one point in their existance. In fact, I had some custom shadow boxes made to hold just my pocket watches. Those themselves were works of art; quartersawn oak, and pegged mortise and tenon frames.
 
Posts: 101 | Location: San Antonio, Texas in the USA  | Registered: July 25, 2006
posted
James nice collection of military pocket watches.Do you got a photo of the shadow boxes?
 
Posts: 523 | Location: Northern California in the USA | Registered: November 23, 2008
IHC Life Member
posted
I'll see if my wife can take a photo or two of them.. They just arrived about a day or so before I had to leave the last time I was home. I'll be home again In September and will mount them on the wall and at that time can take some really good shots of them.
 
Posts: 101 | Location: San Antonio, Texas in the USA  | Registered: July 25, 2006
IHC Member 1291
Picture of Buster Beck
posted
James I'm 25 miles N of Tyler in East Texas.

Are you stationed and in the service or are you working for a private contractor??

regards,
bb
 
Posts: 6363 | Location: Texas in the USA | Registered: July 27, 2009
IHC Life Member
posted
Hi BB,

I am civilian contractor and haven't been in Tall 'Afar in over 3 years now. I need to change that. I am in Baghdad currently although have traveled back and forth to Afgahnistan and other local places. I'd like to host a Texas GTG maybe this next year. I've got a few friends (mil watch collectors) across the US and overseas that want to visit and could have enough for a nice GTG and tour of Old San Antonio (as well as the new Smile) and see some military watches in the flesh. Would also be nice to make a daytrip up into the Texas Hill Country, visit the Museum of the Pacific War (The Nimitz Museum), eat some good Tex-German food. Wink and drink some local beer. What do you say? Are you up, for coming down to SA?
 
Posts: 101 | Location: San Antonio, Texas in the USA  | Registered: July 25, 2006
posted
Michael,

Just to round out Buster's answer... Celestial navigation calculations (known as sight reductions) are all based on UTC/GMT. To save the nav a step in his reduction (i.e., converting local time to GCT), the Army Air Corps/USAAF/USAF issued each a GCT watch which was daily set to - and always kept at - GCT. The 'GCT' markings on these watches are a reminder that that is the time kept on the watch.


Mike
 
Posts: 24 | Location: Spokane, Washington in the USA | Registered: January 30, 2010
IHC Life Member
Site Moderator
Picture of John J. Flahive III
posted
Jim,

Any time you get sick of those military pocket watches, you can send them up to BC. Big Grin

Great collection, really awesome. Mine is about halfway there, but you give me something to shoot for.

I have a bunch of military wristwatches, but I know nothing about them as I inherited them. If I take some pictures, can you help me out?

John III
 
Posts: 1744 | Location: Wisconsin in the USA | Registered: October 17, 2005
IHC Life Member
posted
quote:
Jim,

Any time you get sick of those military pocket watches, you can send them up to BC.

Great collection, really awesome. Mine is about halfway there, but you give me something to shoot for.

I have a bunch of military wristwatches, but I know nothing about them as I inherited them. If I take some pictures, can you help me out?

John III


Thanks John,

I have a hard time letting go of watches. Only when I have extras of the watches do they allow me to move them out. Post the photos of your watches or send to me and if I can, I'll identify them for you.

My email is quattroassi at aol dot com
 
Posts: 101 | Location: San Antonio, Texas in the USA  | Registered: July 25, 2006
posted
I was researching, I know this is an older thread. Here's mine. Any additional insight would be wonderful thank you. pictures and desc.


Warm Regards,

Adam J. Dubilo
Founder | AdamVintage
 
Posts: 1 | Location: Greater NYC Area | Registered: February 08, 2018
IHC Member 163
Picture of Mark Cross
posted
On the topic of GCT navigational watches, were they handled the same way as railroad watches?

Specificially, did they have to be plus/minus 30 seconds per week? were they hacked/set to a master clock before a flight?

I don't believe I've ever read of procedures or requirements that these watches had to adhere to for use, as they were, for all intents and purposes, nothing but railroad watches in military guise.

Regards! Mark
 
Posts: 3730 | Location: Estill Springs, Tennessee, USA | Registered: December 02, 2002
IHC Member 163
Picture of Mark Cross
posted
Well, I found the requirement for the Army wrist watch.....
"The standard called for a dustproof or waterproof casing; extreme temperature resistance; a high-quality, minimum 15-jewel hacking movement with a power reserve of 30-56 hours and a tolerance of +/- 30 seconds per day; and a black dial with white numerals and demarcations."

I'm sure the navigation pocket watches were a bit more strenuous, but +/-30 seconds a day is pretty tight for a field piece.

Regards! Mark
 
Posts: 3730 | Location: Estill Springs, Tennessee, USA | Registered: December 02, 2002
IHC Member 1291
Picture of Buster Beck
posted
Mark I'm sure in the US that military requirements were much the same throughout the branches and requirements were strictly adhered to regarding inspection, maintenance, number of jewels (specs), etc.

Here is a historical account of GCT/GMT for the interested and historians (Google);

Greenwich Mean Time or GMT is clock time at the Royal Observatory in Greenwich, London. It is the same all year round and is not affected by Summer Time (Daylight Saving Time) clock changes.

When the sun is at its highest point exactly above the Prime Meridian, it is 1200 noon at Greenwich.

GMT is also a time zone, used by the United Kingdom of Great Britain and Northern Ireland {UK} when Daylight Saving Time is not in use, from October to March.

The Greenwich Meridian (Prime Meridian or Longitude Zero degrees) marks the starting point of every Time Zone of the time zone map.

Every 15° longitude represents one hour's difference in time: (24 x 15 = 360, the degrees of a circle). You can work out the time at every location on earth if you know how many degrees it is east or west of Greenwich.

Where is Greenwich, England?

Longitude 0° 0' 0"
Latitude 51° 28' 38"N (North of the Equator)

GMT is still widely used as the standard time against which all the other time zones in the world are referenced.

GMT was originally set up to aid naval navigation when travel around the globe started to open up with the discovery of the “New World” (America) in the fifteenth century.

Greenwich was a royal park and palace on a hill to the south of the River Thames east of London.

In 1675 the great race to create accurate maps for navigators had begun and Charles II offered the land to The Royal Society for Britain's first national observatory. Christopher Wren was commissioned to design the domed building.

John Flamsteed was appointed the Astronomer Royal. British mapmakers began to set Longitude from Greenwich and in 1884 it was adopted as the Prime Meridian.

With the introduction of the railways (railroads) in the mid-nineteenth century, Britain needed a national time system to replace the local time adopted by major towns and cities.

As Greenwich, due to the presence of the Royal Observatory, was the national centre for time and had been since 1675, the choice was obvious. Nevertheless, time as shown by the clocks at the Royal Observatory was not adopted officially by Parliament until 2 August 1880.

GMT was then adopted by the United States (USA) on 18 November 1883. The chosen moment was at noon, when the telegraph lines transmitted time signals to all major cities. Prior to that there were over 300 local times in the USA.

On 1 November 1884, GMT was adopted universally at the International Meridian Conference in Washington, DC, USA. As a result, the International Date Line was drawn up and 24 time zones were created.

Today, GMT is used as the UK’s civil time. GMT has been referred to as “UT1", which directly corresponds to the rotation of the Earth, and is subject to that rotation’s slight irregularities. It is the difference between UT1 and UTC (Universal Coordinated Time) that is kept below 0.9s by the application of leap seconds.

regards,
bb
 
Posts: 6363 | Location: Texas in the USA | Registered: July 27, 2009
IHC Member 163
Picture of Mark Cross
posted
Thank you, Buster!

My question was what were the contractual requirements to watch companies for navigational military pocket watches used during WW2?

I found and posted what the Army required for wrist watches, but have yet to find what the pocket watches were required to be able to do. I also assume the same was required by other services, but surely it's written down somewhere in official terms. Confused

Thanks for the interesting information. I have read that before in my own research after reading the find book 'Longitude' by Sobel.

Regards! Mark
 
Posts: 3730 | Location: Estill Springs, Tennessee, USA | Registered: December 02, 2002
  Powered by Social Strata  
 


©2002-2021 Internet Horology Club 185™ - Lindell V. Riddle President - All Rights Reserved Worldwide

Internet Horology Club 185™ is the "Family-Friendly" place for Watch and Clock Collectors