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)
The lens is shown with its original metal lens shade and a brass adaptor for a bayonet mount (unknown) which fits over the original factory M-39 screw mount (probably to fit a Zenit-3 or Kristal camera). The lens is handmade with a milled aluminum body. This lens appears infrequently and probably not many were made.