Based on what I learned from OEM Glass, Bloomington, Il, 800-283-2122, but have not yet confirmed based on enough survivor Camaros, the front windshields were often within a month of the car's build date; however, is was not uncommon for the side and back glass to be date coded 1 - 3 months before the car's build date.
JohnZ....is your windshield dated Jan 1969, and the rest of your glass Dec 1969 glass?
Rich69rs....sounds like your glass date codes also follows this trend.
I replaced my glass during the restoration. The windshield (W/S) had been replaced some time ago before my resto. I followed what I learned to date code the W/S one month prior the car's build date and matched the date codes on the rest of the glass. My Norwood 69Z build date is 05A, the W/S is dated April '69, and the rest of my glass is dated March '69.
