I think if you read the CRG glass dating page, in early 69 (January) each glass plant would also etch a code for the plant that produced the glass.
10 = Lathrop CA.
http://www.camaros.org/glass.shtml
Not entirely correct; maybe you missed this part..
"...The "-xx" suffix on the LOF date code is the plant code. "-10" indicates the source was the Plant 10 Lathrope, CA LOF facility that supplied primarily the Van Nuys, CA Camaro assembly line. A "blank" code (no plant code) was used by Plant 8 that supplied all windshields to both Camaro factories, as well as tempered glass primarily to the Norwood, OH assembly line. "
I've never seen a glass date with a 'glass plant' code (on my '50s - 60's cars), but then we don't see too many VN/LA produced cars here, which is why I asked the question about the '10' referenced in an earlier post...
Oh.. and the CRG glass section I believe has been updated fairly recently (since I read it)...