The MK-65 was the precursor to the Mk67, 150mm F10, with silvered spot secondary that never needs collimation, and is very light in weight. Mine is in as-new condition, with a Questar-like star-test. It has the standard 1.25" right-angle mirror diagonal with in-built helical focusser.
I also have a JMI NGC SC focuser which set-screws right onto the rear cell and gives fine crayford focusing to 1.25" oculars with the 1.25" prism diagonal and Takahashi low profile compression ring. 2" oculars will only come to focus in straight-thru mode.
Looking to trade the whole the whole setup, with finder and Yak-leather case, for a like ETX 105 less Autostar. Or sell the scope with standard accessories for 550, and 150 for the JMI & prism.