so that's Italian threaded, yes?
If the threads were in good shape then yes.
As you’ve said they are in poor nick and the shell width is pretty out of spec for anything but particularly for Italian, I wouldn’t put it past being a bsa shell that’s had a tap run through it the wrong way.
Actually, had to google it because I wasn’t sure but French thread shells are 68mm with two right hand threads.
Hold on and I’ll see what the actual thread diameter is...
Just checked this. The old Bottom bracket tightens up clockwise on both sides, so that's Italian threaded, yes? I had thought when I took the old BB out I had unscrewed both sides anti clockwise, but assumed I just got in a muddle and remembered wrong as I was told it's a British Built frame-maybe it is is not what it purports to be, just tried a 27.2 seatpost and that doesn't seem to want to fit either...