The English "Half-chronometer"

J.W. Benson "Observatory" watch made by Tavannes and
described  as a "Half-chronometer" as was the English made
Benson "Field" watch and many others.

The English description of a watch as being a "Half-chronometer" is, perhaps, a rather grandiose name for what the Americans termed an "adjusted" watch meaning a watch adjusted for temperature as explained in this Wikipedia entry.

This does not mean that other watches will not cope adequately with changes in temperature but that the "Adjusted" or "Half-chronometer" watch has been rigorously tested at extremes of temperature and adjusted to minimise errors.

Unfortunately most good quality English watches, particularly those by Benson, Rotherham and other good makers in Coventry and London plus most imported from Switzerland before the late 1930s and signed by English resellers are not marked "adjusted" so it is only possible to establish if they are by tracking down contemporary adverts such as the following.

From a J.W. Benson Sales catalogue from the late 1930s.

J.W. Benson movements in Dennison cases.

Large numbers of Benson cases were made by Benson Bros[i] (no relation) of Liverpool, but carried the J.W. Benson mark and for solid gold and silver the London assay marks.

A witness mark (just to the left of the case screw hole)
showing that the movement does not belong in this case.
Note the Dennison safety bow on the case.

Benson watches from the 1930s with “standard” sized movements by Tavannes are frequently seen on eBay in silver cases by Dennison, most of these are marriages probably using movements that originally had a solid gold case. These frequently have witness marks from other movements visible on the case as illustrated here (I don’t buy these watches except for spares so the example shown is the movement from the watch below placed in a case from a Waltham watch).

Some however do not bear witness marks but could still be marriages with cases originally from Tavannes watches.

A 1933 Tavannes movement for J.W. Benson in
a Dennison silver case hallmarked 1933

Whilst Benson could have used Dennison cases when short of their own, for quite a while I considered that the majority of these Dennison cased watches were marriages but then saw some with provenance covering 40 or 50 years and I began to wonder, whilst I am very sceptical[ii] about family history, a relatively recent history (when the owner was not trying to sell) probably precludes a watch having been recently re-cased.

Having done some research[iii] I found that the Benson Bros business, including the contract with J.W. Benson, was purchased by Dennison in the early 30s, case making was transferred to Handsworth whilst the original Benson Bros operation was turned over to repair work.

This makes more sense of watches from the 1930s occasionally having Dennison hallmarks. The date of the transfer is not known but was certainly complete by 1934. All of those that I have handled without witness marks showing re-casing, are hallmarked 1933 apart from one, the only datable Swiss Benson I have had from from 1934. So probably these watches came during the transfer of the business.
 

The back of the watch shown above.

The Dennison case shown here is confirmation of this as the date of the movement (from the serial number) matches that of the case. Also the case is not typically Dennison of the period as it lacks their normal patented “Safety bow”, as do all of the gold and silver cases in my mid 1930s J.W. Benson sales catalogue.

It is also possible that the case was originally made for Benson but was sent to Birmingham for assay due to a queue at London or it was made for another third party and diverted.

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[i] Previously the business founded by of R. Samuel, Benson Bros from c1894 and from 1902 owned by J.B. Eastham.

[ii] Well justified I think having been told several totally implausible histories saying for example that a hallmarked watch from the 1920’s was 19th century and the hallmarks were wrong, a London assay having been stamped with Birmingham date marks, because “it has to be that as it was definitely Great Gt… Grandad's 21^st Birthday present” - although not engraved as such .

[iii] Primarily from Priestley “Watch Case Makers of England”, NAWCC Spring 1994.

Dating Movements by Cyma & Tavannes

I recently had a query on dating these movements so have posted the answer here so I'll not have to do it again.

The serial number on these movements are under the dial as show to the right. My dating is based on a reasonable number of watches, listed below, in hallmarked silver or gold movements. The sample is heavily biased to watches retailed by J.W. Benson, largely because other retailers frequently used Swiss hallmarked silver cases which do not carry a date mark. Benson appear to have switched from Revue to Tavannes in about 1932 the database is only good for the 1930s.

It must be remembered that a movement might not go straight into a case which itself may have been on the shelf for a while so there will be some overlap, also the hallmarking years of the various assay houses are not in line with each other or the with calendar but the difference is small and the date is likely to be accurate to plus or minus a year.  (updated Feb 2017)

Serial	Date
4,322,549	1908
12,487,883	1919
14,708,666	1919
13,079,475	1921
14,262,246	1924
15,485,579	1926?
15,485,952	1926?
15,939,146	1926
17,482,498	1929?
16,624,975	1930?
17,865,828	1932
17,886,973	1932
17,888,724	1932
17,888,811	1931
17,889,975	1932
17,899,152	1931
17,899,219	1932
17,889,918	1932
17,902,501	1932
17,903,525	1932
17,903,625	1932
17,908,930	1932
17,909,034	1932
17,909,035	1932
17,944,833	1933
17,944,871	1933
17,966,044	1933
17,970,131	1933
18,045,354	1935
18,045,567	1935
18,050,727	1935
18,052,802	1936
18,055,283	1936
18,055,497	1936
18,055,498	1936
18,055,544	1936
18,066,750	1935
18,070,392	1936
18,076,649	1936
18,090,883	1936
18,112,605	1937
18,112,379	1936
18,113,219	1937
18,141,556	1937
18,146,434	1937
18,146,664	1938
18,199,372	1937
18,240,750	1938
18,245,978	1938
18,246,001	1938
18,252,273	1940	Benson stock?
18,253,220	1939
18,256,774	1938
18,265,158	1938
18,268,000	1940
18,276,566	1947?