MTOM ..... f:8 / 500 mm Mirror Lens ..... factory : OOMZ /Leningrad, USSR
year : 1961 ..... serial # : 610694

notes : The factory that made this Maksutov 'catadioptric' mirror lens is: 'OOMZ' which stands for the "Opytniy Optiko-Mekhanicheskiy Zavod" (Experimental Optical-Mechanical Factory) and also known as the "Russkie Samotsvety Zavod", which translates to "Russian Gems Factory".

In October 1962 this plant was incorporated (along with 'GOMZ', 'Kinap', and 'Progress') into a new industrial union, later -- well known as "LOMO". (Thank you to Dmitry Kopp of KMZ for this information)