Stampings on Birmingam engines.

A NOCcer has asked me about 2 stampings on his Birmingham (Bracebridge St) built Jubilee engine. He writes:

I've included a photo that shows the numbers 32'31 and a letter T high up on the RH crank case half. The 32'31 must refer to ignition timing, but surely that wasn't stamped on every engine? The stamping looks to have been done at manufacture.

The first question is easy to answer – '3231' (the extra apostrophe is just random) is in fact the Shop Number used in the factory to identify the engine before it was installed in a frame along the production line. If found to be good (some weren't!), the frame number was copied onto the engine above the primary chaincase – hence original bikes have matching Engine & Frame numbers. (I think there is too much interest riding on this - leading to liberal use of grinders & number stamps).... 60 years have passed since then, anything could have happened, resulting in an engine transplant! The Shop No system was discontinued at Plumstead.

That leaves the matter of the letter 'T' stamped just below the barrel. Our writer thinks it alludes to Timing, as it just happens that Jubilees are timed at 32° before TDC, fully advanced. More likely it's the engine builders identity. Any other ideas?