[Richard]

Hmmmmmmm, glass can be professionally polished with cerium oxide. Just because the people who worked on your windows did not know how to get them clean, doesn’t mean they can’t be cleaned.

And as a chemical engineer, it takes some pretty strong and special acids to actually etch glass. Think about all the wicked chemicals that are only shipped in glass. Much easier to mechanically etch with a blaster, but that didn’t happen inside the double panes.

Please do more investigation on glass polishing before you give up. You might also look into formic acid to clean the residue off the inside of the glass. It is often used to ensure laboratory glassware is super clean.