MTO (MC) 3M-5CA 500mm F/8, a lens created by russian company LZOS following the Maksutov design from russian optical engineer Dr. Maksutov ( hence the MTO 3M-5CA getting its nickname 'Maksutov' ).
Type: (MC) 3M-5CA
Focal length: 500mm
Weight: 620 gram
Focus mechanism: Manual
Aperture mechanism: Fixed
Product page for the lens on the LZOS site can be found here
While it is still being sold, one site said production on the lens stopped in 2008. Probably the only way to find out the exact age of the lens you have is by the serial number. If paperwork was included with the lens, manufacture date or batch information might be included.
Hope that helps.