The little ESOTEC. But little is here meant by the standards of the very late 70s...
The front flap hides the Power-On button as well as the Class A / AB and speaker switches.
Supposedly the stereo version of the Ma-5 monoblock but the techniques used are fairly different. And there's "only" one transformer, "only" the same amount of smoothing caps and a heat-pipe system instead of the forged heatsinks of the Ma-5.
Still - "only" is here meant by the standards of the very late 70s !
Sorting by numbers, one may think that the Sm-6 would be closer to the Sm-7 - well, no : the Sm-8 is much closer to the 6 than the 7 is from either. The 7 being a rebadge of an older unit, this makes sense.
In fact the 8 is an upgraded 6, with two small smoothing caps added, a market-related optional black face, a blue meter window and the Quarter A topology.
Seen the other way around, the 6 is a smaller 8. But then, the 8 doesn't have two sets of inputs (Normal / DC), nor input level pots, nor pure Class A all the way like the 6 has...
So who's the little one ?
A real Sm-6 here.