If this helps, the windows were installed as part of new construction in 1991.
I'm afraid the stamps you showed us don't tell us what you have. There should be more stamps on the balance; we will need to see a clear picture of each one. Or just the whole balance in one picture, if the stamps would be clearly visible from that angle. Thanks!
We're getting closer! I'm confident that the stamp we need is on the tab there, at the bottom of your
recent picture. I can almost make out a "9," but not the rest of it. Could you show me a clearer picture of the stamps on that tab?