Attached is a copy of a page from the 1965 Ford Car Facts Book (printed August of 1964) which shows in the Mustang Section for Fastbacks that the Rear Glass on a Fastback has Tinted Glass as "Standard". I believethat on Jim's previous Post, the Tinted Glass shown is for the Windshield and Side Glass onlt.
So, according to this, all 1965 Fastbacks came with their Back Glass Tinted.
Hope this helps,
Bob