I emailed the seller and he said that the bike is made of Columbus steel, did'nt specify the type though. I found an 83 Bianchi catalog and they had several bikes with painted rear stays and Columbus tubes; the Nuovo Racing, the Tipo Corsa, or the Super Leggera which uses a combo of SP and SL tubing (is this a good or a bad thing?). I might be missing some options, but hopefully someone who knows more will chime in