Do Not Open Windows at Speeds in Excess of 120 MPH

Do Not Lower Windows at Speeds in Excess of 120 M.P.H

I happened upon a classic car cruise on this fine summer evening. I am going to get the placard with the 120 MPH warning for my Prius. It’s not authentic to the VW bug I saw it in, but there were cars that had such a sticker because the rear window might blow out at high speeds. I suspect it’s an inside joke among the classic car crowd.