Information from toz35.blogspot.com
First of all – I have heard and seen many ways of spelling and writing of this trade mark, but I would say that right variant of spelling and writing is «MTs». «Ts» must be pronounced together and not separate (the same spelling as in the word «tsarism» [‘za:rizem] or «tsar» [za:]). Not «M-T-S». Many of you say «MU55» or «Vostok» or «Baikal» and I don’t know why. I suppose that all USSR weapons were exported under one name (one exporter) «Vostok» and you know these all products as «Vostok» no matter TOZ35 or MTs55.
Also, MTs55 was a family of free pistols produced in USSR from 1961 to 1990 by TsKIB SOO. TsKIB SOO (Russian abbr.: «ЦКИБ СОО» or full name «Центральное конструкторско-исследовательское бюро спортивного и охотничьего оружия». Full name in English: «Central Design and Research Bureau of sports and hunting weapons»). It is not so easy as may noticed. It is not a factory or something like this. It is state research bureau. Only high quality limited editions. The bureau has own website (unfortunately fully non-informative).
The series of MTs55 free pistols:
- MTs55, 1795 pistols produced from 1961 to 1980;
- MTs55-1, 466 pistols produced from 1971 to 1990;
- MTs55-1M, 514 pistols produced from 1981 to 1990.