The 6B/159 watch (Mk. VIIA)
(Spec : RAF Pilots Watch)
The RAF expansion schemes from 1934 to 1939 provided the opportunity for forward planning for the RAF and this was accelerated after the declaration of war in 1939.
One item which needed to be procured was a hacking watch for navigators to assist with accurate navigation. This needed to be simple to use for dead reckoning navigation.
British and American air forces held joint meetings regarding the design of the American A-11 watch, which in Britain was to be sourced for the RAF and labelled the 6B/159.
The watch was to have a hacking facility, and the Weems second setting rotating bezel had provided this in a robust way, helping to simplify avigation for about 10 years. The American Weems A-11 was initially manufactured in accordance with US military specification 27834, published in August 1937, and the British 6B/159 met specification G.535.
During the meetings, the Air Ministry deemed the A-11 Weems model too small at 27mm diameter, but Longines had produced a larger 34mm version since 1937 which the Air Ministry liked.
However, the 27mm diameter type A-11 was standardised by the United States Army Air Forces in May 1940, and had leaf hands as did the commercially available second setting watches at the time. The bezel lock is at 2 o’clock, and the bezel has a noticeable slope.
The British Weems 6B/159 with specification Mk. VIIA needed to meet the following requirements of Building Specification G.535 :
The movement needed to be wound by the crown instead of using a separate key. The movement should run for a minimum of 36 hours (fully wound). The hands should be made of blued steel and the case should have a rotating lunette. The case could be made from steel, chrome or hardened brass. The dial needed to be light silver or white (like enamel). The deviation needed to meet the following requirements: after three hours +/- 3 seconds, after six hours +/- 5 seconds, after twelve hours +/- 8 seconds and after 24 hours +/- 15 seconds.
Eventually, about 7000 Weems 6B/159 watches were produced to this specification, and they were individually numbered xxxx/40 on the case back. These watches were ordered in early 1940, and delivered in the first half of 1940.
There were five manufacturers of these timepieces; Longines, Omega, Jager-LeCoultre, Zenith and Movado. Omega, Zenith and Movado used the same case.
The Longines Weems is thought to be the most common, and the Movado the least common.
The original January 5, 1940 order note for 2000 Omega Weems CK 2129 watches, 6B/159 is shown below. This shows a leather strap sewn into place, and notes a 16mm lug width. All watches were issued on leather straps.
A compilation of the issued versions of both the American and British watches is shown below, courtesy Konrad Knirim.
WW2 era Weems models.
Longines 6B/159 Weems
The heritage of the Longines Weems dated further back than the Omega, which was made in 1940 under licence, and about the same number (about 1900) of these watches were made, compared with the order for 2000 given to Omega above.
This watch is examined in more detail here.
The Longines Weems 6B/159 models are numbered in the approximate range 1800/40 to 3700/40. A typical serial number of the watch movement is 5934652 for case 2340/40. This makes the movements a few thousand earlier in production than the smaller A-11 Longines Weems, e.g. with a serial number 5938556 for case 40-662.
6B/159 Longines Weems cal 12.68N with original flanged crown, and blue spade hands.
The spring bars were fixed, and pigskin straps were fitted.
The bezel is wider and flatter than the A-11 watch of 1940.
The back cover is marked with “Goldsmiths & Silversmiths” who procured the watches. “AM” stands for the Ministry of Air Force (Air Ministry).
The case serial number for all five manufacturers of 6B/159 watches runs sequentially, and the model above is 2340/40.
Observed serial numbers for the Longines models range from at least 1893/40 to 3691/40.
A few dials have been seen with an open 6 and 9.
Civilian models exist outside the 6B/159 order, and serial number 5992610 is shown below, with baton hands, from about 1940. The case back was sterile.
Although the A-11 Weems was a smaller diameter, the larger diameter watch was also used in the Americas, some with a sterile case back, and some LeCoultre models with blued propellor hands, from order no. 42-10905-P, labelled A-11.
Below is an US Navy Academy embossed dial from the early 1940’s, with baton hands.
And, below is a RCAF sub seconds issue with a white dial. Serial number 6155664 calibre 10L of about 1940.
And, a black dial model from about the same time, with smaller sub seconds, sold by Antiquorum in December 2004.
Finally, a 34mm version with no bezel lock, and the cal 12L fitted, serial number 6481439, about 1942, and dial with baton hands.
A French publication on wristwatches for navigation illustrates a bottom lock bezel. These were more common on the Longines Weems models of the mid 1930’s. Also shown is a rare white dialed Waltham Mk. Vlll watch, the 6B/234.
ZENITH 6B 159 WEEMS
The Zenith Weems has thicker numerals on the bezel. It has one spade hand and an hourglass syringe hand. The Omega, Zenith and Movado 6B 159 all used the same case, with a cam lever set into the case at 4 o’clock to lock the bezel.
Image ; Copyright Core Vintage Watches, by permission.
The model number 6B 159 is engraved on the case back without the / as for Longines.
The movement was the Zenith 106, and case numbers are seen in the range 5586/40 to 6301/40. Zenith movements are sometimes re-cased in Movado cases, (and vice versa), as the cases are identical.
This extract from Konrad Knirim’s book shows the entire watch, including the movememt
Another photograph of the dial. The second hand is seen with, and without the counter weight.
MOVADO 6B 159 WEEMS
The Cal 150MN movement was used in this model, with a spade hour hand and a tapered syringe second hand, as for the Longines.
Observed case numbers range from 333/40 to 1579/40, with either stainless steel or plated bezels.
A Movado on a Bonklip strap is shown below.
Sometimes the Movado Weems is seen with 83817 on the dial in purple dye, or faded purple dye as shown on the 2 examples above. There is no explanation for this.
The caseback, with the earliest known serial number.
The example below does not have the 83817 imprint on the dial.
Here is a sterile dial, a MoD re-dial with a narrower 4, and without SWISS MADE at 6 o’clock
The movement is the Cal 150MN.
The bezel lock mechanism housing for this case is shown below.
Movado later produced a black dial Weems model in 1950, with cathedral hands, 17J cal 127 movement and about 36mm diameter.
OMEGA 6B 159 WEEMS
This watch is ref CK2129 has the Cal 23.4 SC movement, with 2000 ordered as noted above.
Omega case numbers have been observed in the range 3634/40 to 5580/40
The dial has a spade hour hand and a thin needle pointer second hand.
The dial is signed OMEGA with the Omega symbol.
Movement 23.4 SC
Shown below on an A.F.0210.® strap.
Photo credit IG the.vintage.collector
LECOULTRE WEEMS (6B/159 AND A-11)
LeCoultre made 34mm diameter watches for the RAF labelled 6B/159, and for the USAAF labelled A-11. The cases were identical.
The 6B/159 case numbers observed are in the range 7155/40 to 8530/40, and about 600 USAAF A-11 watches were made.
The 6B/159 case back read “S. S. & S” for Samuel Smith & Sons, who procured the watches for the Air Ministry.
The LeCoultre models have the most dial variations of the 6B/159 Weems models. Blued leaf hands were used, but the dial can have radial numbers, and can be sterile.
The bezel has numbers every 5 minutes, the only 6B/159 watch to do so.
As for the Movado, 83817 in purple dye is sometimes seen on the dial.
Below, sterile dial, with radial numbers, and 83817 on the dial for the top example.
Below, signed dial with non radial numbers.
Cal 450 movement.
A USAAC model is shown below, case number 468. Many case numbers were not engraved on this series, other than the LeCoultre 5 digit case number.
The Konrad Krinim article is shown below, image courtesy the author.
Longines Heritage L2.608.4
The demand for the Weems model by collectors led to Longines reissuing a Weems model.
Below is the Longines Heritage version of the watch, model L2.608.4, released in 1995 as a limited edition of 3000.
This has many design elements taken from the above watches, but is slightly larger at 36mm rather than 34mm, and has the bezel lock at 2 o’clock.
A variety of cases and dials were used, here is a black dial gold version, also available in stainless, and a two tone dial also was produced. Perhaps 1000 of each dial were produced, white, black, and two tone.
Non Weems bezel
The next version of the 6B/159 watch was a non Weems bezel version, issued later in 1940.
Below is the LeCoultre version on an original A.F.0210. strap.
Image courtesy watchuseek forum user : David SquaGly.
The strap is stamped A.C. for the manufacturer Associated Cutters.
This watch will be covered in a later post.