Crank wind film advance with fully coupled COPAL shutter designed to prevent double exposure.  Apparently some later models were fitted with plastic gears to quieter the "coffee grinder" noises emitted at film advance.  Some photographers report that these gears are apparently prone to failure under heavy use however I have owned two of these cameras and have had no problems so maybe it's a case of how hevy handed the user may be.  The shutter release button featured both a turn to lock mechanism and an internal thread for standard cable release.

Yashinon 4 element 80mm f3.5 taking lens and a 3 element f2.8 viewing lens as fitted to the early model Mat-124g cameras.  The addition of an indicator window in the focus knob to remind the photographer of the film type was a handy feature.   The Mat-124gs was fitted with adjustable film back plate to allow the use of 220 roll film as well as the standard 120 (12 x exposures).

Accesorys for this model included the Wide-angle and Telephoto add on lenses which were applied directly to the Bay1 filter mount.  I have tried both these lens sets which provided that the user is "sensible" about aperture selection (ie. Not wide open) will provide a moderate degree of width or magnification with reasonable resolution.  One should not expect to make "big blow-ups" where these add on's are used.