I want to learn:
Attached is a picture of the rear side window with its strap. How is the window regulated with the strap? I don't see any means of securing the strap to enable the window opening to be regulated.
My dad had a coupe like that in the '70's. It was either down or up. Just like the photo you posted.
It is not "regulated". It is either up or down.
Front & rears just drop down - our '19 Centerdoor's center windows straps have two small holes that grab a small button on the door for two adjustments. I cannot verify if that was stock or a modification by the previous (2nd) owner.
A new centerdoor owner myself. Here’s what I have learned. You pull the window up with the strap. There is a lip on the outside bottom of the window. Once the window is up, you push the bottom of the window outward and the lip hooks over a matching lip on the body.