I currently own a 4 channel MX5050 with the separate electronics (2X stereo) and transport, which seems to be direct drive, though i thought it was not. I did have a couple of the older 2 channel ones, one at least with the silver face and IIRC at least that one was flat belt drive. I also have an interest in 2, ARS1000 decks which are probably in the silver face era and also have flat belts. These were playback only, decks for radio station automation , but still 5050 related transport.
Is there anywhere on here or elsewhere on the web with a chronology with images of the various models?
I know in the one series there are 5050, 5050B, B2 and B3 plus all the other variations and models.
BTW on those PRB #s, though the ones listed earlier relate to round belts PRB does list flat belts in the same inner circumference. Not sure if the width would be right however.