Yes, buff log book shows engine and frame as JM23 159. I am sure this was done when registered or re registered in 1942. Most likely as whoever or which ever workshop did not know where original frame number is, they also did not know what cc it was as engine is down as a 350cc which makes it even more likley to me that it was someone in a workshop without knowledge of BSA models.
Lower lug on front down tube is where my correct frame number JM19 300 is stamped.
I am going to apply for a new registration using correct frame number at some point, but am intrigued as to what went on in 1942 with the bike.
The continuation buff log book of 1949 was registered to Alan Douglas EDE, 32 Airman hq. Raf Hullavington. Chippenham Wiltshire
I expect I will not find anything more out except lots of mistakes were made at that time with details of my bike.

email (option): Mcsutcliffe67@gmail.com

Marcus, do you know if the JM19 frame register still exists ? If so, it would provide a useful double check on any information given in the engine books.

I've looked at, for instance, the KM20 frame ledger and the KM20 standard and deluxe engine books and they're not always consistent.

As an aside, here is a 1940 mention of the scheme for local purchase of civilian machine. As far as I'm aware, the threatened compulsory scheme never came.

Rik, thanks for giving my query some thought. I assume frame register does exists as VMCC date certificate quotes frame as being assigned as a M23 with a tally number. If that is what you mean?
I suppose what this is all leading to is, do I keep all the wrongly registered buff log book, engine number stamped on frame, wm21 engine, etc as all genuine and real history, which I believe it is ! Or would it be viewed as just a story with nothing to back any of it up. I like to have bikes with interesting history.
Hence hoping to try and find out more.
If I re register bike on original factory frame number which I could, then I feel everything else that went on with the bike is lost and not relevant any more, which would be a shame.

email (option): Mcsutcliffe67@gmail.com

Marcus, the JM19 and JM 23 engine books (first column is engine number followed by frame) are at the VMCC and the JM24 frame and engine books are both there...but I don't know if the JM19 frame book is...there are gaps and missing items. The next year's KM23 shared a frame with the KM22 and that book still exists.

I had a look at these for someone, a long time ago, but BSAs are not my speciality and I probably missed a lot. I think that you can still visit the VMCC and view the microfilm copies but they no longer allow the actual ledgers to be handled. Maybe you'd see some clues that others have missed or not been able to interpretate.

If it does still exist, the JM19 frame book will list all the frames and show which type of engine was fitted, together with number.

My personal feeling is that I'd rather have a V5 that reflects the correctly-located and factory-stamped frame number. Did you say if you have a current V5 ? If not and you use the old logbook, it will be retained by DVLA anyway and if they send an inspector, there is a risk that you could end up with a 17 digit VIN stamped on the frame.

Hi Rik.
I think I will apply to DVLA for a age related reg for my M23. I have the frame info from VMCC already and can get a dating letter. The frame info states it was designated as a M23.
Like you say, it is better to be registered on correct frame number, I have a JM23 engine but it needs work. Still, a empire star is a good BSA to have although I will not restore it in anyway.

email (option): Mcsutcliffe67@gmail.com