GM Window Glass Decoding

Keeping a collector car as original as possible is very important to many enthusiasts. They search for the correct date-coded parts with the correct casting codes, etc. For the extreme stickler for originality, even the manufacturer's codes on the window glass are important. The codes should match the build date of the vehicle and are as important as any other correct part. But how can you tell if your codes are correct? It's easy—and we'll show you how with this batch of codes from 1963 through 1972. We are using both 1965 and 1969 GM intermediate musclecars as examples.


First establish the build date of your vehicle from the trim tag on the firewall or cowl. The glass codes should indicate that the glass was manufactured before the vehicle. If your engine is original, you can use the casting dates on the block and heads for build-date referencing as well. Here are the codes you need:

Year/Month of Manufacturer
1963-C/Jan-N


1964-G/Feb-X


1965-J/Mar-L