Is it the sort of quality frame you'd expect to see; i.e. double-butted Columbus? I can't believe how little clearance there is between the tyre and the seat tube. Looks like if you picked up a bit of sticky tarmac from the road, it would touch the frame!
The Master frame I alluded to above has absolutely no serial numbers on it anywhere, and no sign of any having been filed off. I even checked the forks where they go inside the head tube. It's extremely light though, definitely not a gas pipe dressed up snide copy.