Later years added a few more designations for laminated stocks that may include the main model, plus a designation for the stock, & possibly even the color of the stock. I couldn't keep up with those.
For instance; M77VBZ
I don't believe there was a red one. The tang safety was discontinued before there were too many laminates.
The "Z" is green laminate.
You are correct on your other two assumptions.
Chet15