Thanks to all for the replys! I plan on some mods to the frame (add a seat. move the pegs, mini apes, add rear brakes, and rake the front) and I wanted to be sure that I am not messing up a vintage frame.
The rear axle mount welds match the rest of the frame but the adjuster is homemade (bolt welded to a thick washer). It's hard to tell if the frame has been modified. The guy I got it from was told it dates from the 70's (?).