Cleaning Window Glass

I have attached a photo of one of the rear quarter windows of my 1990 5.0 hatchback. There are some kind of deposits on the glass that I cannot remove. I tried all glass cleaners, isopropyl alcohol, lacquer thinner, Blechwhite, 409 and plastix. Any idea what these deposits are and how I can remove them?

Looks like hard water stains to me. A cleaning vinegar, stronger than regular vinegar and usually says cleaning on the label. Plus use #0000 steel wool after it is soaked for a couple of minutes with the vinegar. Be sure to rinse it off well, since if left on for a long time may put extra wear on the rubber seals in the area.