One of the 1964 men's models is the M 69-2.
The M 69-2 came in a one-piece stainless steel case with a white dial along with luminous hands and dots at the hour markers.
Under the dial is a Swiss-made Hamilton 688 movement.
I recently acquired an example of an M 69-2 that was not running and had a broken stem so the crown would come off when you set the time. The 688 is an ETA movement and shares the stem with several other ETA movements so I had a spare on hand for an easy fix. So really the watch just needed a good cleaning and a crystal replacement.
One piece case are usually opened with a diabolical looking claw tool called a crystal lift. The tool compresses around the circumference of the crystal and squeezes the diameter enough that you can pull the crystal off. It goes back on the same way. Just release the pressure and the crystal expands into the bezel, making a waterproof seal.
Since the case is one piece, the stem has to be two pieces so you can pull the movement out the front. In the shot below, you can see the female portion of the stem. It engages a corresponding male portion in the crown and allows you to wind the watch or set the time. If you pull the crown really hard it will pop out of the female portion. However, you can also lift the movement out with the crown in place - if you're careful.
Servicing the movement is pretty straightforward and like the 686 movement in the Gary I recently showed, the 688 also has an adjustable hairspring stud so the beat error can be fine-tuned.
And here's a shot of the finished product - all cleaned up, running great and with a new crystal.
It's a very sharp, clean looking watch with a classic 1960's styling, I think.