Carreras certainly had the same rears, sharing the same as Saracen. dependant on year it either had a clamp on seat clamp or not. some came with rear rack mounts some didn't, dependant on batch. Also some had tange tubing some had a modicum of Reynolds, dependant on model year and model, of which I cant be sure without it in hand.
of course it could be anything, its best guess from me.
The canti hanger is though unusual in that is it made of, what looks like, two straight milled plates with the stop mounted between them as against the cast half elliptic most bikes, including the Carrera shown above, Oranges and the Sarries I can find of the period. Equally it could be the 'light' in the photo!
I'm just a 'player' amongst gentlemen but have a passing interest in the problem solving of the time.
Respect to your academic knowledge, though, I'm sure you're right
Like a fish ever needed a bicycle anyway...MTB: '89 MF Alu Team Pro,'88 Muddy Fox Courier,, '92 Orange Elite (now 17"!), '04 Kona Fire Mountain (now Son's), '96 Muddy Fox Ranger home-build (son's), Specialized RockHopper '92 (Ad's retro-build) ,'02 Kona Scrap Special Edition OB (3rd Son's), 1989 Orange Clockwork (Gone!?)
ROAD 2013 Orange CarbO ,2012 Basso Devil (3rd son's), Colnago CLX3.0 Di2 self-build