Hello Gentlemen and thanks for all the interest, thoughts and replies.
First, the carb in the pics is not from the mystery motor. It's an old Amal from another project. Sorry about the misleading clue.
Regarding the markings, I haven't opened it up yet, so only clues are external. These are:
1) On the gear lever plate, it appears to be "21109" and "R" in the diamond. I'm assuming Registration symbol, maybe British?
2) On the cylinder base and case, right side are matching serial numbers, "10921". On the left side above the mag case on the cylinder base is what appears to be a foundry mark that makes me think BSA maybe? Not clear enough to really make it out, just evokes one of the BSA logos and I'm a BSA guy from way back.
3) Finally, on the mag cover, upside down it reads "6V 15/17W ULA1CR25" Then what appears to be a "D" in a circle.
There are a couple other marks as well, another D in a circle and some numbers that appear to be part numbers to match cases, eg twin "17"s and a "15" in a circle.
The fact that there is no kicker makes me also think some type of bicycle/moped application?
I mostly picked it up because it is what it is and it's a cool little motor! Seems to be all there with exception of carb and pipe. I welded (poorly) up a little base from scrap metal and mounted it as shown. If I can't figure out an application for it (or find someone who is desperately seeking this particular motor for a project) I'll just take it apart to see what's what, repair if possible, and either get it running or just sit it on a shelf to look at.
Thanks again for all the help!
Regards
Mike