I believe they were made by Sinclair along with the front ones too (I think I've read somewhere that the Sinclair ones are lighter than the usual British Leyland items)
From what I've seen the Sinclair ones have no markings and BL ones would have to conform with various regulations.
Definitely not off a Honda Cub - I have one and they're completely different

I can't guarantee overnight success, but I'll put a brand new 1 pence piece on the line and bet that they've been used on something... even if it's something nobody's thought of like a Honda C90... 