It's like a top sekrit code! It's better than Pig Pen!
From the surprisingly high-information marks on the windows I've deduced that my windscreen, rear screen, and all my side-windows were made in Q1 of 1964. The quarter-lights look to have been replaced later -- they're actual Triplex, and while the dots under the letters are a bit unclear I think the windows are March 1970 (for the driver-side quarter-light) and March 1975 (passenger-side).
Absolutely fascinating. Now I just need to find out what sort of glass would have been used originally...