Wristwatch restoration, servicing and repair

Hamilton 6B (Hamilton Cal. S75 S)…

More military watch action on the blog, this time from Hamilton.

(Click pictures to enlarge)

Hamilton was founded in Lancaster, Pennsylvania in 1892 by a group of entrepreneurs whose aim was to only build watches of the highest quality. Located on a 13 acre site, they produced high quality pocket watches, specialising in railroad watches where accuracy was important. Their involvement with military watches began in World War I, when they were producing wristwatches for servicemen using calibres from women’s pendant watches.

During World War II, production of consumer watches was halted and they produced nothing but military timepieces; wristwatches, marine chronometers and deck watches for use by US Navy and other Allied Forces. More than 1 million wristwatches were sent overseas.

Hamilton supplied watches to the British Military from 1965 until 1976. As well as the 6B featured in this post, other models included the W10, a time only manually wound watch in a one piece tonneau case, and a Valjoux 7733 powered chronograph in an asymmetric case.

You may also see the 6B referred to as the “Mark XI” as it was made in the same style, and to the same specifications, as the IWC and Jaeger Le Coultre Mark XI watches also issued by the British military.

(More information here)

The caseback has the familiar military markings; the Broad Arrow symbol, the designation number, the date of issue (1967), and the serial number. The 6B at the start of the designation number denotes that this watch was issued to a member of the Royal Air Force. The watch has fixed springbars to provide better security when in use, and notice too that the caseback has a shallow ‘waffle’ pattern worn into it. This is caused by extended use of a NATO strap – a one piece strap originally fitted to the majority of military wristwatches.

The caseback on this watch was extremely tight and obviously hadn’t been opened for a long time, but once opened, underneath the protective dust cover was a Hamilton S75 S in good condition.

The 6B was fitted with one of two calibres, the earlier watches were fitted with the cal. 75, the latter the cal. S75 S – a new version upgraded to include a hacking function. The base for these calibres was supplied by ETA, the cal. 2390, but was extensively reworked by Hamilton to become the cal. 75.

The watch arrived in running condition, but hadn’t been serviced for many years. Only the screw for the ratchet wheel showed signs of corrosion, and on closer inspection was an incorrect size and was replaced.

Cosmetically the watch was in decent condition, though the crystal was cracked and needed to be replace. Judging by the difference in colour between the dial and hand lume, the hand lume had been replaced at some time, though this isn’t uncommon for military watches, as the original lume tends to dry out and crack, eventually falling out of the hands altogether.

With the movement serviced, the case cleaned and a new crystal fitted, everything was back in order.


** Many thanks to Stephen Brown for letting me feature his watch on the blog. **

One Response to “Hamilton 6B (Hamilton Cal. S75 S)…”

  1. R. Crichton Says:

    rich, thanks so much for your work with time pieces… love a good watch! i have a 1959 hamilton 505… cool thing is that it says electric on the front and
    ticks… it is early enough that it says pat. pending on the face. it is the earliest of 5 electric or electronic watches i own. all are in mint shape and all are running but one. 3 are FME Kent swiss/french… and one is kent with a rodenia watch works on the inside. love them! looking for a bulova accutron from the end of the 50’s or beginning of the 60’s the ones that hum instead of ticking.