I just was offered a Mamiya 645 body, prism finder, 120 back w/ 80mm 2.8 and 210mm lenses for $200.00 US. Condition rough with some light scratching on lenses which may not be too signifigant for my use. I want to get into MF cheaply. Serial number on the body is L77940. I can't figure out which model 645 this is. Can anyone advise me on which model this is and maybe how old?