According to the research report by Rich Fields, it seems that my PPG quarters are probably not original, but are from a Firebird. The LOF quarters, which are still installed on the car, one is Nov. and one is Dec. They are both from plant 10, and both are M75 Flo-Lite glass. The LOF left vent window is Oct. from plant 6(marked 16) M55 Plate. The LOF passenger door glass is Aug. from plant 8(blank) M55 Plate.
While total Camaro production was fairly close for all 3 years, A01 option nearly doubled in 68 and more than tripled in 69. IF rarity was a factor, and coupled with Ed's response, I would think that the glass is probably original.
You people are doing great work here, there's a lot to see and learn on this site and this forum. I'm soaking up as much as I can. Thanks