The Yashica 12, manufactured in 1965, the Mat 124 in 68’, and the Mat 124 G in 71’. The 12 is the only one that just uses 120 film. The others took 120 and 220. They have an on-board battery-operated meter, and the 124 and 124 G have a crank. There are only two differences from the 124 to the 124 G, gold battery contacts (hence the G) and the chrome lens frames were replaced with black plastic. Many photographers go for the G, which is more expensive, but many argue the 124 is a better built camera.
Key features of the Yashica Mat 12,124, and 124G:
• Lens: 80mm f/3.5 Yashinon twin lens reflex
• Shutter speeds: B, 1 to 500.
•Exposure Meter: CDS match needle
•ISO Film speed range: ISO 25 to 400.
•Focal range: 3.5′ to infinity, to avoid Parallax error don’t get too close to the subject.