Don't have a good guess but am subscribing for updates! The "fish-mouth" stay ends are often associated with Bernard Carre but many other FR builders adopted that detail so it's not the best clue (plus the bridges and stay caps have no "Carre" look to them. IMHO). Since you correctly (I think) ID'd these as Oscar Egg lugs, this and the brake bridge may be the best clues, and also might point toward Swiss as Juvela indicates, since that's where Egg originated even tho the lugs were more highly popular with Brit builders than others.
Last edited by unworthy1; 11-03-19 at 01:01 PM.