AMC Date Coded PPG Glass
AMC used PPG and their products including Herculite & Solex on their vehicles. All of the glass was dated coded by manufacturer. Some of the codes are unknown like PPG's internal (in house) codes.
You will find the stamping on variety of places on the glass, windshields, door glass, back glass. Door glass lower corners as most 1/4 glass, while windshields and back glass dead center bottom. A sample would be like this 71-74 AMX & Javelin rear glass:
AS2 M20.7 26 23
Herculite was a brand name of PPG, as was Solex
AS2 (some are marked AS-2) is for door and rear glass; AS1 (or AS-1) is for windshields.
AS are standard glass codes (American Standard) used by Society of Automotive Engineers (SAE, also found on many glass). The "AS1") were laminated windshields which were required to standard 70% light transmissibility & be impact resistant. "AS2" was similiar requirements, but had to pass side impact reqirements, 70% light transmissability and was tempered.
Second code, "M" is the Model Number. M20, M25, M27 are internal PPG unknown codes. .7 indicates thickness of the glass of that particular kind. M25 usually reserved for windshields while M27 side & back glass & tinted. Some have a space between digits, others do not, in other words some might be marked M20.7 or M20 7 or M207. The digit after the internal PPG code is thickness:
The second to last codes above (26)
are manufacturing plant of origin.
Most American Motors glass came from three plants:
25 Greensburg, PA
26 Crestline, OH
27, Tipton, PA
so above glass is from Crestline, Ohio for instance.
The end codes/far right (23) are month & year (2=Feb, 3=73). The above glass is a back clear glass pressed in February 1973 for a 1973 AMX.
Some AMC glass like below example will have five digits (far right digits) like 26109. If so, first two are the day, second & third are month and last number year. So 26109 is translated to October 26th, 1969.
This above glass is a passenger tinted door glass from a 1969 Javelin, the glass pressed October 26th, 1969.
DOT 18. DOT=Department Of Transportation while18 was PPG's Pittsburgh, PA location. Stamped on most AMC glass.
This is a passenger door glass from a 1968 AMX. It's what happens to most AMC door glass, the windshields, rear glass and 1/4 glass survive better. PPG "sand etched" the numbers on but they do not last forever althogh this one is still partly readable, the actual dated faded with time.
There are few, if any, reproduction door glasses for American Motors vehicles. What has been reproduced is 68-74 AMX & Javelin windshields but upper rib tint incorect, about $250 for a variety of auto glass shops, glass is correct snug fit; 68-70 AMX door glass, but has holes in bottom to mount then to door tracts (WTF!) and rear 68-70 AMX & Javelin back glass has been reproduced, about $450.