Mauidj, Well, you asked, so I will answer. The Mk2 and Mk3 are quite different from each other. I know it sounds like the Mk3 would be just a later version of the Mk2, but that is not so. Both tables were marketed at the same time, although the Mk3 came along last, at the end of the "vinyl era" and dawn of "perfect sound forever". To start with, the Mk3 has the highest torque motor ever used in a turntable sold to the public, with the possible exception of the Denon DP100, which was a Japan-only product for Denon. The Mk3 has more elaborate motor control than the Mk2 and a 22-lb platter, also very heavy for a direct-drive. It also has all its electronics housed in an outboard chassis; the main chassis supports only the huge motor and the platter.
The Mk2 has an 8-lb platter and a less powerful motor, notwithstanding the fact that it is also a great turntable when properly set up. The outboard Power Supply feeds three regulated voltages to the remainder of the electronics, which are onboard the main chassis along with the motor. The Mk2 is right up there with or ahead of any other vintage direct-drive of that day, was considered a high end product, got raves from HP, etc.
In their day, the Mk3 cost about twice as much as the Mk2 (about $2800 vs about $1500). Ergo, fewer Mk3s were sold, and they are quite a bit more rare than the Mk2. Also, those that own a Mk3 tend to keep it, which adds to the rarity of finding one for sale. Many Mk2s and Mk3s were used and abused by radio station DJ's because of their incredible rapid start and stop capabilities and their durability.
