Originally Posted by
ldorchester12
the seatpost is 26.8mm. I don't know very much about road frames but there is a shimano BB if that tells you anything also. so I believe that would mean it's english threaded?
Not necessarily since Shimano made sealed BBs in both BSC and Ital, but you could probably both measure the width of the shell (68mm or 70mm?) and/or find the notation on the BB unit that tells you (may require removal for that).
I can't tell what brand those lugs are, but the seat stays are single-taper and a 26.8 could be a plain-gauge 531 seat tube,OR Aelle tubing, OR a Japanese tube like Tange or Ishiwata. I still think the other details (tho there aren't many) point to a Brit frame so if that seat post is correct size, I'd lean toward the plain-gauge 531.
Still just guessing.