There is a whole series of 407/.. numbers in the post war key cards, I think this one is 407/18, presumably a rebuilt machine using any good spare frame available restamped to create a serviceable machine with a new identity?

Rob

email (option): robmiller11(a)yahoo.co.uk

Ah, I checked for that, but could not find it somehow!

Lex

email (option): welbike@outlook.com