PPG Glass Date Codes?

[JoeG]

musclecarKid,
I pulled out two original side pieces of PPG glass that came off my '69 chevelle to check the code.The rt frt.PPG glass reads flow lite [27-29],the smaller rt.r.PPG reads flow lite[26-49]


Now I'd say it's a rating of the glass--at first I thought it was a light transmission rating, but then I found some info on [noise reduction ratings ]and [sound transmission class] on safety tempered glass ,and it's rated by thickness of glass, manufacturing process etc.---the rating system is similar[ 27-30 ]--[26-47]---[25-29] and so on.---Just some more info to kick around----JoeG