The Kowa Six MM was the second in a trio of medium format Kowa cameras (preceded by the Kowa Six and succeeded by the Kowa Super 66). Released sometime in the late 1960s to early 1970s, the MM version of the Kowa Six added a mirror lockup mechanism as well as multiple exposure capability. Unfortunately the internal gearing involved in film advance, which had a reputation for being softer metal and prone to wear, was not updated. The whole Kowa Six lineup was firmly in that category of camera known as the "poor man's Hasselblad", sharing company with the likes of Bronica and others. The Kowa Six fit that roll quite well and the MM with its modest improvements made the camera an even better choice for photographers looking for a medium format SLR without paying Hasselblad prices.
It is worth noting that the Six MM was succeeded by the Super 66 and that camera offered interchangeable films backs - a big improvement for those who favor the utmost modularity in their medium format systems.