The Praktica MTL 3 is an East German SLR made by Pentacon, using the 42mm screw mount. It was produced in high numbers between 1978 and 1984. It is said to be based on the LTL 3. It's a solidly made camera with some rather crude and advanced features.
This is the best part about this camera. The MTL 3 has a very robust metal curtain shutter. It moves vertically and is likely to work some 35 years after its production. (I have one that appears to be in full working order today in 2018) Speeds are B, then from 1 to 1/1000 sec. It has a separate position for use with electronic flash units; this is "about" 1/125 sec according to the camera's manual. It's metal curtains are not known to get punctured easily as cloth shutters often do.
The standard lens supplied with the camera was a Pentacon 50mm f/1.8 lens. It has a m42 or Pentax thread. There's a switch on the lens to use it on auto or manual. The auto option allows full aperture composition even when the aperture ring is set to, say f/8. The lens is multicoated and has a 49mm filter thread.