I think all of the Yashica TLRs used 120 film. No difference in the actual film and paper backing between 120 and 620, but they had different spools and thus were not interchangeable. The only interchangeable backs that were available for them was, I believe, a gizmo for the model 635 that would allow it to use 35 mm film. The model number seems to indicate its ability to accommodate both 6x6 (120) and 35 mm film. All of the others, until they started using the name Yashica Mat on later models, perhaps in the early '60s were designated by letters A thru D, I believe. I had a couple of them and actually did some weddings with one of the later YashicaMats.

I have a non working "635" that I got in a yard sale for $20 but it doesn't have the 35mm adapter. Was worth a gamble for the price. All of the Yashica TLRs that I ever handled were solidly made and the lenses were good enough with medium format film to make 8x10s all day, and an occasional wall hangar.