might be AS1
. AS1 refers to the clarity of the glass. #1 is used for windshields. It's interesting that we see this on almost every windshield, but a Google search shows no single, clear explanation of it's meaning. Many references to it being the lower limit on the windshield for tinting, but I don't find any 'official' explanation of that. Searching for American Standard turns up the bathroom fixtures company.
ASI and AS1 seem to be used, according to this document
, AS1 is the proper marking for glass that meets specific testing. (pg 23) Pg 24 says the line above the AS1 mark is the limit of tinting. Note: This is only a draft document.
AS is the mark from the American National Standards Institute
ANSI-American National Standards Institute