These windows are Andersen 400-series windows, also beautiful windows!

Actually, those appear to be Andersen's 100 Series. The 400 Series has a different glazing bead, and the A-Series doesn't have an exterior glazing bead.

Thank you Quasiexpert, but these ones are indeed the 400 series from Andersen.

OK, not gonna say I've never been wrong. But I've been in Andersen service for going on 15 years, and the only 400 Series casements I've seen with a flat glazing bead, plus butted rather than mitered, were the triple pane units from the early to mid 80s. Also the reveal around the sash appears to have the 100 Series black sash weatherstrip. But if these are your windows and they say 400 Series on the PID, props. Perhaps they're some sort of special order coastal product.