Does anyone know the difference between contracts which are prefixed with a 'C' and those with an 'S'.

Thanks

Andy

email (option): a.tizzard@btopenworld.com

Andy, there was a theory that the C stood for Copper (contract) plates, and S for steel plates, but what the real significance behind it is I'm not sure??

I would think more like the rivets where they were affixed with were Copper or Steel, as the copper plates are really brass and not copper.

Some of the steel plates were also affixed with copper rivets, so that theory also doesn't really hold?

But why they would have used it as a contract prefix is a real mystery to me, maybe Rik or Jan can shed more light to it?

Cheers,

Lex

email (option): welbike(a)welbike.net

Eh, yes, the C for a Copper (or brass actually…) contract plate and S for Steel is only a rule of thumb, not a real theory. And there was one exception to that rule: the Welbike contract S/1946 still had a brass plate.

But I do have a theory that this C – S has something to do with the allocation of the census numbers. It has always been assumed that there is a “mathematical relation” between a motorcycle’s frame number and its census number, but there was no proof of this theory. The mathematical relation is:
“census number” – “frame number” = “checksum”.
Within a contract the checksum should be a constant.

The RASC contracts: The pre-March 1940 (approximately) RASC motorcycles had their census number stamped on the engine crankcases. I have studied several examples (Royal Enfield and other makes), and have come to the conclusion that there is absolutely no “mathematical relation” between the RASC census number and the frame number of a motorcycle.

The very early RAOC contracts: “almost matching” numbers: I have had the opportunity to study the BSA keycards. These BSA cards only contain RAOC numbers, no pre-1942 RASC numbers. After having studied the BSA “key-cards” intensively, I have come to this conclusion: it is clear to see that the RAOC tried to have matching frame and census numbers (this means they should have the same checksum for the complete contract). But during the early contracts (until contract C/5110 inclusive) some small errors occurred. Because the RAOC used a “consecutive” numbering system, the error remained the same for huge blocks of census numbers. This means that the checksum also remained the same for huge blocks of census numbers, but not for the complete contract. This also means that a “calculated” census number is very often a few numbers off...

Later RAOC contracts: matching numbers: From BSA contract C/5610 onwards the checksum stays the same for the complete contract. Census numbers can be calculated using the checksum formula.

The S-contracts: married-up numbers: While I was researching the census numbers enigma, I noticed something important. The receipt card for the Royal Enfield contract C/11081 (This was the first WD/CO contract, the RASC census numbering system had been integrated in / replaced by the RAOC system a couple of months before) states “married up” census numbers. This is not the same as “matching”, which only means that the checksum is constant. “Married up” means that the last two digits of frame and census number are identical, which makes it much easier to avoid mistakes. All WD/CO contracts (and the contemporary WD/RE contracts) have “married up” numbers. The Norton contract C/11082 also had married up numbers, but this wasn’t noted on the receipt card, and may have been the odd exception. But: in early 1944 the Ministry of Supply started using S prefixed contracts, and all the S- contracts (all makes) have married up numbers! Three exceptions: the Royal Enfield contracts S/1546 (WD/CO) and S/6602 (WD/RE), and the Triumph contract S/2114 have “married up” numbers, but only the last digit is identical. The second last isn’t. Errare humanum est...

Conclusion: with the exception of only three contracts, we can say that all the S-contracts have numbers where the last two digits are “married up”. Royal Enfield also had four C-contracts with married up numbers (starting with the first WD/CO contract, and there was even a note about these “married up” numbers on the receipt card of that first WD/CO contract). Norton had one “married up” C-contract (an exception...?). Other manufacturers had none!

Hope this helps!
Jan

email (option): wd.register@gmail.com

Pre-war Army orders were placed on behalf of the War Office by the Directorate of Army Contracts and their system seems to have been continued by the Ministry of Supply when it was founded in 1939 (with the intention that it supplied all three services).

However, inter-service rivalry and jealousy being what it was, it affected not only operational efficiency but also procurement. The Air Ministry seems to have held out for several years before allowing the MoS to purchase its vehicles and I'm not sure that the Admiralty ever fully gave in as RN vehicles don't appear in MoS ledgers.

Under the old DAC system, it seems that the first letter of the description was taken as the contract prefix. 'Motor Cycle' was always written separately in those days and became 'C'. I've seen 'B' used for Bicycles, Bodies and Bearings. 'T' for Tractor, Trailer, Truck and Tank etc.

Most vehicles used 'V' (for vehicle ?) Spare motor cycle engine contracts were genererally 'E' but sometimes 'C'. Norton contract 7353 is sometimes shown with a 'V' prefix and sometimes with a 'C' so presumably someone slipped up somewhere. There are a couple of 'V' contracts for Big 4 outfits too so maybe they weren't sure if they were 'Motor Cycles' or 'Vehicles'?

At some point around mid-1942, the Ministry of Supply began to order vehicles for the RAF and RN as well as Army and presumably had to merge several systems. In the MoS ledger there is purely a numeric system used with no letter code which perhaps means that the 'S' prefix was applied later to indicate a (Ministry of) Supply contract.

Due to the manner in which demands overlapped contracts (and sometimes post-dated them), together with the varying lead-in times from different manufacturers and the associated issue of census numbers, it is quite difficult to be precise about when the changes occurred. Broadly though, it was purely an administrative change and didn't seem to affect the vehicle or the end-user.

Edit. I started this reply before I went off to eat and didn't see Jan's reply. Nothing that I've said conflicts with that but I do think it likely that the changes he notes were also a result of a new collective ordering system replacing the old DAC way of doing things.

Thank you all for your input, Henk suggested the forum and as always it has provided valuable information - however I just knew it was not going to be a simple answer!

Andy

email (option): a.tizzard@btopenworld.com

Andy, if this sort of thing interests you then I'd recommend a trip to the National Archive at Kew. There are dozens of Ministry of Supply files and probably heaps of useful information to be extrapolated....It just needs someone who's not busy for about a month...

And then there's the 'V' contracts Ron

email (option): ronpier@talk21.com