Rear axles were painted as an assembly; cover and brake drums in place but no lines. Pinion flange was masked. Paint was a glossy black. Yes the drums were black too.
I found this at the Camaros.org site.
I would imagine the code sticker was applied to allow easy pull from stock without trying to read faint stampings that were painted over, sticker on the pass drum, is what I found on my LOS 1968 car, little yellow w/black two letter code matching the stamping on the rear, How the heck it stayed on the car all those year was amazing. (Come to think about it low miles must have been a factor Would 76k in 1983 be low miles? 5k per year by 1983.)
Jim W