Hi All
Thanks for your replies so far. Bozman, I look forward to your contributions, Rollfaster, thanks for the image, I've had difficulty finding earlier bikes, and this will help sort that out.
Bikewhorder, Mr. Columbia's site contains an excellent listing of frame numbers by year, and I certainly couldn't have started this without that help, and the frame numbers he subsequently supplied, which I acknowledge in my post.
http://ichef.bbci.co.uk/news/624/cpsprodpb/DDB9/production/_92616765_heinz1.jpg
Where I came in here is that I recently bought a G519 Westfield Columbia (MG154118 / K8) missing a lot of parts. From Mr. Columbia's list I could see it was late 1943, but nothing more. Liberator has a page dedicated to these bikes, and from there I learned that 1943 saw a lot of detail changes, so I became interested in understanding when these occurred by frame number.
http://www.theliberator.be/militarybicycles.htm
From the internet, and later from people here, I recorded various details (S/N, BB/N, frame type, Eclipse hub code, chainwheel type etc.), and will be putting out a table of these details for Westfield G519 shortly (the Huffman Dayton one I compiled at the same time is already on the CABE here
http://thecabe.com/forum/threads/huffman-dayton-g519-frame-numbers.100336/
Mr Columbia said on his site about the BB numbers between 1936 and 1945:
This starts serial numbers being stamped on frame under crank hanger. The letter preceding the serial number indicates year of manufacture. Often there will be a separate letter with 1 number near or above the serial number. The meaning of this is not fully understood but all evidence to this time indicates that this has nothing to do with the year of manufacture and the serial number. Best guess is this was a part number of the crank hanger forging itself for factory use to identify the part before it was brazed or welded onto the frame.
I recorded the '
separate letter with 1 number near or above the serial number.' and soon realised that there was a pattern that showed these to be a separate year/month code for the production of the frame. I also saw that this system applied to all Westfields at this time. I had more examples to hand, and an interest in that specific dating problem which allowed me to make the link not available to Mr. Columbia.
The final breakthrough came during this CABE conversation on Westfield Compax:
http://thecabe.com/forum/threads/1944-columbia-compax-military-model-folding-bicycle.99850/
This allowed me to collect numbers for other frame types (and showed people were interested!). It allows year /month dating of the frame production, and has also given an insight into production techniques (Work in Hand, when the final serials were stamped) and shown that, probably due to the complexities of Wartime production, the prefix to the main serial number is not as straightforward as you might think, with, for example, the prefix W appearing in addition to MC, MG, G etc. This is still only a fraction of 1% of all Westfields produced at the time, so there could be other codes out there too.
I hope that helps explain what I'm tying to do.
Best Regards,
Adrian