Mamiya 645 Pro serial numbers?

Hey,

Does anyone know how the serial number system works for Mamya 645 pro film backs? Also I have a couple of viewfinders with a gold sticker on each. 1 says RA the other SK. Is this where they were quality controlled or something?

Thanks,

Dan

IIRC, the gold stickers are closer to Mamiya's system for manufacturing date, moreso then the serial number. It's similar to Canon's dating system.