Nice Theory...but i've also seen classical upsweep arms like that get replaced when they get rusty,which means they could have just had the arm replaced...your theory is more likely tho...Streetview HERE.
Be careful, because the newest powerdoor models have NO vents and they fit in GE M-400A1s if powerdoor got replaced, so it's best to look at what type of latch is there, if it has no latch...its a "Split door" if it has a latch then its a powerdoor.
There's a 1992 GE M-400A2 that had vents on the original powerdoor, but it burnt out not too long ago and my friend replaced the door, the new one has NO VENTS!
These likely don't have new doors because the doors match the rest of the fixture, but that's an intersesting thing you bring up about the no vents on the A2 doors. There are no A2's around here, so i never knew that.
Yes very often the colors have different shade from whole fixture and door...and even some cases where I live we have a lot of bronze colored fixtures (some say brown) we see grey doors on bronze....but I have also seen vice versa which is grey fixture with bronze powerdoor!
We also have GE M-400A3s too, and they don't have vents either.
I have also in an unrelated topic seen mis-matched door and top housing...for example recently I saw one a bronzed AE 113 top housing have a new AE 115 grey door Yes the 115 and 113 are interchangeable! Kinda fun to spot.....
Looks like Joslyn arms? Defintely 6ft 1-1/4" but they look kinda dark for aluminum. I don't recall seeing medium fixtures on 1-1/4" arms here either, but there are plenty of small size fixtures on 1-1/4" arms here.
There's a 1992 GE M-400A2 that had vents on the original powerdoor, but it burnt out not too long ago and my friend replaced the door, the new one has NO VENTS!
We also have GE M-400A3s too, and they don't have vents either.
I have also in an unrelated topic seen mis-matched door and top housing...for example recently I saw one a bronzed AE 113 top housing have a new AE 115 grey door Yes the 115 and 113 are interchangeable! Kinda fun to spot.....