If you come across any of the kits shown below, consider yourself lucky. They are rare and, therefore, quite collectible!
The exquisite NOIX Models resin kits, somewhat understandably, fetch very high prices on eBay.

Classic Airframe kits

E.P Original

Any Alphaflight kit (Br.20 and Z.506 not shown)

Any NOIX Model kit (C.29, M.39, M.52 & MC.72 not shown)

Any Italian Classic kit. (RE.2000 not shown)

Misterkit Fiat G.50 & G.55 resin kit

Flashback S.79