Soemtron calculators and Daro office machines were manufactured by V.E.B. Buromaschinenwerk Sommerda in Soviet East Germany.
The company no doubt grew from that part of the German hi-tech industry that found itself in the Soviet bloc after the war. Boris Chertok's fascinating and detailed autobiographical history of the Soviet rocket programme "Rockets and People" contains interesting stories of the technololgy that he helped to identify and repatriate back to Russia from exactly the region around Sommerda, where V.E.B. Buromaschinenwerk Sommerda was subsequently established.
The Soemtron 220 offers an insight into the state of electronic technology in the Soviet bloc during the late 1960s and early 1970s. The Soemtron 220 was introduced in 1966 and seems to have remained in production until 1977, a very long time. In the West, first and second generation machines were obsolete and out of production in 4-5 years at the most, and often after only 1-2 years.
The 220 is a competent 4-function, 2-memory machine and is built with core memory, discrete transistor logic and Nixie tube display. As noted above, all of these technologies were well obsolete in the West by the end of the 1960s.
Mike Hatch's excellent Soemtron site contains a wealth of information about the Soemtron 220 and other machines from V.E.B. Buromaschinenwerk Sommerda.
The soemtron.org site contains extensive general, historic and technical information, together with a full reverse engineering of the 220, with logic diagrams and circuits.
Please visit soemtron.org for any and all further information.