Took a few more photos today of my original.
Mirror back has the rectangular raised support, a letter D molded into the plastic and the dimmer lever. Also note the H cast into on the windshield bracket, I have another that I picked up at a swap meet that has the letter I cast. Maybe some sort of date code
Finally I have one that has a longer neck on the windshield mount. It does not have any letters cast into the bracket. The intermediate shaft and the mirror itself are identical to my original.