Greeting all,

I know this subject has been mentioned previously but I do not think a thread has been created devoted solely on the topic. In the interests of thourouness I would like to discuss.

This is a new acquisition. We all know the story of these watches but I will give a brief history.

These Zenith deck watches were issued to the British government in 1942 and used as deck watches throughout the war. After WWII (1950’s-60’s) these watches were held in Herstmonceux Castle in Sussex where some changes were made. Some of the deck watches underwent dial changes and new rear case NATO markings. The dials were changed to “decimal dials” mainly indicating 100 units per minute which would assist with scientific study and making quick mathematical time calculations. I have seen only Zenith and Hamilton examples with the dial changes so far.

I have some questions hopefully some members can answer:

What Zenith caliber was used for the watch and how many jewels? All the sources say 15 jeweled movements but was a 16th jewel originaly added for the sweep second hand? One source states these movements were the same as WWI RFC Mark cockpit watches; those had sub second dials not center sweeps.

Were any examples other than Hamilton and Zenith changed for this purpose?

Does anyone know the approximate number of timepieces that went under this change? It seems like they are very common with a high number of them changed over, but how many do you actually need to help with some math problems?

I would love to see all the members with such a “decimal” example come forward and post their photos and watch information. I know the topic has been touched upon here and other watch forums but would like to make IHC 185’s thread THE place for plentiful and excellent information on this watch variation. Thank you.

Rear case old H.S.3 marks crossed out and new NATO marks.

Broad arrow marked movement

In its case.

Any help to answering my questions would be a great help! Thank you all.

Michael, your Zenith watch has the Cal. 19-34-3-T, it has 16 jewels (originally 15), the extra jewel added for the centre second. 2 watches of the same type are depicted on pages 428 and 429 in Konrad Knirim´s book "Military Timepieces", these being the Hamilton and Zenith, also suggesting only these two types had a dial change.
The regulations as to how these watches were to look, were published in the MoD Def Stan 66-4 (part 10) which is now obsolete and cancelled. An extract from the standing orders are also on the bottom of the pages. Basically these watches were used by the Royal Navy during the war and were redailed in the sixties by Watch Dials of Burford, commisioned by MoD Chronometer Section at Herstmonceux Castle in Sussex and given its new NATO reference number
The watch was thereafter called a "Watch for work studies"


This is the list of the Def Stan that were available;
66-4 Watches, wrist, divers
===========================
Part : 1
Status : Cancelled Dated : 30-Nov-90


66-4 Watches, chronograph, wrist
================================
Part : 2
Status : Cancelled Dated : 30-Nov-90

66-4 Watches, Stop watch 1/100 second
=====================================
Part : 3
Status : Cancelled Dated : 29-May-92
Superseded by : Def Stan 66-46/Iss 1

66-4 Watches
============
Part : 4 Watch, wrist, electronic, general service
Issue : 4 Dated : 29-Feb-80
Addendum
12 Pages

66-4 Watch, wrist, electronic, navigator, luminous and non-luminous
===================================================================
Part : 5
Issue : 3 Dated : 19-Jun-81
Addendum
12 Pages

66-4 Watches. Stop watch, 1/10 second
=====================================
Part : 6
Status : Cancelled Dated : 29-May-92
Superseded by : Def Stan 66-46/Iss 1

66-4 Watches. Stop watch, 1/5 second/1/100 minute
=================================================
Part : 7
Status : Cancelled Dated : 29-May-92
Superseded by : Def Stan 66-46/Iss 1

66-4 Watches. Stop watch, 6 second sweep, calibrated in yards, general service
================================================================== 
Part : 8
Status : Cancelled Dated : 29-May-92
Superseded by : Def Stan 66-46/Iss 1

66-4 Watches. Stop watch, 1/5 second, dual second hands
=======================================================
Part : 9
Status : Cancelled Dated : 30-Nov-90
66-4 Watches. Watch, pocket, work study (continuous running)
============================================================
Part : 10
Status : Cancelled Dated : 30-Nov-90

66-4 Watches. Watch, pocket, general service (non-luminous)
===========================================================
Part : 11
Status : Cancelled Dated : 30-Nov-90
66-4 Watches. Stop watch, 1/5 second, dashboard
===============================================
Part : 12
Status : Cancelled Dated : 29-May-92
Superseded by : Def Stan 66-46/Iss 1
66-4 Watches. Stop watch, 1/100 minute, work study (continuous running)
==================================================================
Part : 13
Status : Cancelled Dated : 29-May-92
Superseded by : Def Stan 66-46/Iss 1

66-4 Watches. Stop watch, 1/5 second (continuous running)
=========================================================
Part : 14
Status : Cancelled Dated : 29-May-92
Superseded by : Def Stan 66-46/Iss 1

66-30 Chronometer. Chronometer, electronic, quartz
==================================================
Issue : 1 Dated : 19-Jun-81
12 Pages
66-46 Stop watches
==================
Issue : 1 Dated : 29-May-92
30 Pages
66-47 Strap, wrist watch
========================
Issue : 2 Dated : 30-Mar-01
10 Pages
Source: http://www.dstan.mod.uk/ (10th. July 2005)

This is wonderful information as always Werner. Thank you for your help and time spent on the subject.

I'm glad we have this data on the forum. Thank you.

Hallo friends,
as Werner 'Jimmy' shows on page 428 in my book I show an EMT Tissot with a redial to decimal, so EMT is the third brand redialed to 0552/521-0243 'for work studies'.
Greetings Konrad Knirim