Circular slide rule watch with packaging, Boucher type, metal / glass / cardboard box, Research Institute for Control Equipment, Moscow, USSR, 1960-1970.
Circular sliderule. Soviet KL-1, Russian manufacture : MATSKM ?
Boucher's style, double sided circular sliderule, with scale in radians on front and long (spiral) scale on reverse. In yellow card box. This is a pocket watch sized, double-sided circular slide rule with a glass face. On the front side there are the two log scales of a standard slide rule. On the reverse side there is a spiral inner tangent scale, a sine scale and an outer log scale. The "sliding" disks are rotated around the fixed disks by a knurled knob and there is another knob to wind the cursors.
Scales and signature style name: MATSKM