Worth the same as any other 1.2 a500
the whole "rare" is just.. well, not rare.
It wasn't worth €45 though, less than half that really, and that's with psu, mouse, modulator etc. ( ie: "complete" system)
Prices vary insanely on ebay but for a basic 1.2 a500 with a 1/2mb expansion and nothing else I can't imagine ever paying more than £10 plus postage on ebay which of course equates to "not many €"
as for 1.2 vs 1.3 I think that's just people saying words because they can say words.