So far nothing but crickets chirping on this topic, eh? I'm not an originality guy, but I'll play along. Here's a pic of my 68 (HARD to get my crappy camera to focus that small).
BUT...I don't have the FOGGIEST idea whether any of my glass is original or not. My entire car is about as far from original as you can get. But I've owned it since about Y2K, and I haven't replaced the windshield yet. I do have ONE factory bird glass. And my windshield is all pitted and scratched all over...it's definitely old.
Our stamps are quite different eh? Especially the print of the font. Mine is like a stencil, yours looks typed. Spacing is all different. And yours has that DW689 and mine does not. What this all means? I dunno and don't care too much...but maybe this helps out a fellow fgf'r who always tries to help others like you do...hopefully it does?