Whatever it is ...it is very elegant.
I have seen the bracket shell, lugs, fork crown and rear drop-outs many a time..but they were used by many builders, but that is meant in no way at all as a criticsm..the bikes a beauty and so well proprtioned..
AND it's my size!
Wish I could be of more help...but this frame is not a beater..or whatever you call a knocking-about-town bike.
Norris Lockley , Settle UK