The Yashicamat is basically a Rollei copy, with a few of the more expensive features left out, but the ergonometrics left in. Crank wind, combined film wind-shutter cock, Rollei bayonet 1 mount for filters. Somebody moving up from 35mm should get better pictures from a properly adjusted Yashicamat than from just about any 35mm camera (keeping in mind the limitations ot a waist-level finder, fixed f3.5 80mm lens, etc.).
The final model - the 124G - was made for many, many years. Basically it's an all-black 124 with a few other styling variations. The "G" stands for "gold" and indicates gold plating on the meter switch contacts, which increases their reliability a little. The meter circuitry is said to have been updated in the G. CdS meter cross coupled to shutter and aperture for match-needle exposure. Rotating pressure plate for both film types: 120 film and 220.
The taking lens is a four element Yashinon 80mm / f 3.5. This lens is generally thought to be a copy of the Zeiss Tessar formula. The viewing lens is a three element Yashinon 80mm / f 2.8; the matte glass has Fresnel magnification and for better focussing, there's a 3x loupe built in.
Flash can be used on all shutter speeds.