Thanks Tom! Yes, you can send the pictures to me, I can post them here.

I wonder if Rob Miller can check if your bike (WM20.35502) and Bob's bikes (WM20.41037 and WM20.78362) and the three engines at the top off this thread (WM20.49952, WM20.57460 and WM20.54713) can be found in the AWM ledgers!

Stay safe everybody!
Cheers,
Jan

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

I've just received Tom's pictures (thanks Tom!). The broad arrow is clear to see, but unlike all the previous pictures, this one is stamped on the frame!



It would be interesting to see more examples, on engines or on frames!

Jan

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

This is what my M20 has Jan. Any idea of the significance of the arrow in the circle on the timing side? Ron

email (option): ronpier@talk21.com

Thanks for these Ron!
In the first picture (drive side) there's another B stamp, as discussed in this thread.
In the same picture, under the WM20 Number, there appears to be a round stamp with "A9" at the bottom (but the stamp seems to be upside down). Never seen anything like this before, but it looks as if BSA used several similar stamps: V213, V227, BSA F5. See pictures below:







The picture above also has a ^51 stamp, as in Ron's second picture. Again not unusual on BSAs:




Ron's third photo (the one you were asking about Ron) appears to have a combination of the BSA F5 stamp and the ^51 stamp... In my opinion these are all BSA factory "quality control" stamps, not military stamps, as I haven't seen these stamps on other makes yet...

Please keep them coming!
Jan

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

Great information as usual Jan. Now that you tell me what the circle is, I can see it. Nice to know that it was some sort of BSA inspection. We just need to know what those pesky B's are?

Cheers Ron

email (option): ronpier@talk21.com

These Bs are indeed intriguing me Ron!

I've just had an email from Bob, who's living in Australia. Bob has visited the National Motor Museum at Birdwood in Australia and checked their BSA for me (thanks Bob!). And yes, bingo! Another one with the broad arrow as described in my first post! The engine & frame number is WM20.46289, I'm sure Rob will be able to confirm that this one is also in the AWM ledgers.




Thanks again Bob!

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

Time for a small update on the (presumably) Australian broad arrow markings. Thanks to the forum members we've discovered some more examples, and thanks to Rob Miller I've been able to check if the respective BSA engine numbers are indeed listed in the AWM ledgers. Here's what I found:
- WM20.35502 (broad arrow stamped on rear frame): not listed in the AWM ledgers
- WM20.41037 (broad arrow with part of a serifed letter M stamp on engine): listed in the AWM ledgers (AMF number 13292)
- WM20.46289 (broad arrow stamp on engine): listed in the AWM ledgers (AMF number 30538)
- WM20.49952 (broad arrow stamp on engine): listed in the AWM ledgers (AMF number 37543)
- WM20.54713 (broad arrow stamp on engine): listed in the AWM ledgers (AMF number 38890)
- WM20.57460 (broad arrow stamp on engine): listed in the AWM ledgers (AMF number 83515)
- WM20.78362 (broad arrow over a letter M over 397 stamp on engine; this is a British Army acceptance marking): not listed in the AWM ledgers

Conclusion so far:
We know that the "broad arrow over a letter M over a number" markings on the WD motorcycle engines (or on the Welbike frames) is a British Army "acceptance marking". See also this thread.
I think it is now reasonable to assume that the "lonely" broad arrow stamp on an engine was typically used by the Australian Army. And it looks as if they also had a "broad arrow over (part of) a serifed letter M" stamp in use.

More examples from down under are of course always welcome! If you don't know how to post pictures here, please send them to me in an email, and I'll post them here for you.

Thanks for your help in resolving another mysterious marking!
Jan

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