I think you will find that the broad arrow (or crow's foot) denote "property of the crown". It was not used exclusively for defence force property.

email (option): cas.vanderwoude@gmail.com

Sorry I can't do pictures, but these are the marks on my 2 WM20 engines domiciled in South Australia

WM2078362 "spare" engine though it's been in the bike over 20 years
In the same location as the pictures, under the front of the tappet chest
Broad arrow, under this a capital M
under this 397
The mark is quite neat & looks like it was all done with the one stamp

WM2041037 original engine, same number as frame
Broad arrow, same position
No other marks

Thanks Bob! Can you send me pictures in an email so that I can post them here?

The broad arrow over a letter M over 397 is a British Army Acceptance Marking. @Henk & Rob, is WM20.78362 listed in the AWM ledgers? I bet that WM20.41037 (only broad arrow) is?

Regards,
Jan

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

Bob has sent me some pictures today (thank you very much Bob!).
Engine WM2041037 has a broad arrow mark.
Engine WM2078362 has a broad arrow over a letter M over 397.




The broad arrow over M over 397 is a British Army “acceptance marking”. See more about these markings in this thread. The interesting thing is that I have never seen this number on a BSA yet. I keep a list of these acceptance markings on the M20, see attached print screen.



On the other engine there is a broad arrow with a corner of a serifed letter M! It looks as if this was also an acceptance marking, but the punch didn’t hit the engine completely… The broad arrows on the Australian engines that I found look slightly different though. Which means that the search for Australian broad arrows goes on!

Cheers, and stay safe!
Jan

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

https://en.wikipedia.org/wiki/Broad_arrow#Origins

email (option): cas.vanderwoude@gmail.com

Evening Chaps’
I have been reading this thread with keen interest regarding the broad arrow stamps, What i have recently discovered is a arrow stamp on the rear o/s chainstay of my 41 WM from contact C7287 Frame number WM2035502, I know quite a few of these bikes went to Australia (V5 states bike was previously registered overseas i’m In Yorkshire) was wondering if anyone knows more about the Broad arrow on the frame i’ve certainly never seen it before? Can mail any members photos cos i’m crap with computers ☹️
Regards, Tom Green.

email (option): rustytomm20@hotmail.com

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