Don’t know if this has any relevance, another stamp not too far away from the other.
https://ibb.co/FHMf0tz
Thanks,
Gino.
BSA engines are literally littered with stampings.
Ones with a broad arrow were done by governement inspectiors.
All the others are normal identity or fit marks done at the factory so that parts which were machined as an assembly can be reunited for final assembly.
The other thing is parts were subjected to testing with a series of go / no-go gauges and in many cases would get a stamp according to which gauge fitted best then when assembled, the assemblers could pick parts that were the best fit with each other.
You will find them all over the inside of the engine.
And then there were date stamps.
Gino, that looks remarkably like weathered Khaki Green No.3 on your top tube...Have we seen a photo of the whole machine and of the frame number ? Is that an original stamping ?
In my experience of ex-WD bikes, it's not that unusual for owners in the 1950s or so to have replaced a damaged / bashed / blown up bike or major component with cheap old ex-WD stock and then simply transferred over the number from their logbook...far less trouble and expense but a puzzle for us, sixty years down the line...
It's a mystery!
It does look like faded green in the photo, I'll take a proper look in the daylight to confirm. There is also some light blue in their!
Thanks for all your input & comments,
G.