Yep to Allegro and other things to note: there's an Allegro serial number database you should be able to dig out in this forum via the search tool, you can narrow down the build-date by comparison and should reach out to the data-master and add yours to his list.
Also this has a Georg Fisher sand-cast BB shell (Swiss made and Swiss threaded), almost certainly is all Reynolds 531, you seatpost should be 26.4 (or POSSibly 26.6).
I have a few random decals (vinyl stickers) you might like if you want to do more of a rolling restoration (someday), I had a batch custom printed years back by VeloCals.
Also note it would NOT have had that under-BB cable routing originally.