Johno, that is your point!! I was of the opinion that it was a BSA TW 32. You already had doubts that it is a regular version for passenger transport trades. Lavrakas pointed out the short side members via PM to me, thank you! So it shall be a prototype. Johno and lavrakas, thanks for your doubts, they have solved the puzzle and made me smarter. In the picture below you can see the side members of the series version.