Greco PU-2s and the letter "A"

These "A" stamped pickups show up from time to time, with no real reason or rhyme. Why did they use an "A" stamp on some 80's Maxon pickups made for Greco?

The only working idea I have is that they wound the "A" pickups in the same place and at the same time as they wound the "Z" pickups. I think they probably didn't want to get them mixed up so decided to use an "A" stamp for PU-2 pickups.

Are all "A" stamped pickups PU-2s? There are also some "A" pickups without "PU-2" embossing in the plates. One more mystery.

The pictured set is from a 1980 EGF-850. The numbers suggest different production dates. Only one has an "A".