1965 Dodge Dart Charger

Ah, thought that might be what you meant. Might have been a Swedish legal requirement; Volvos and Saabs back then all came with retroreflective stickers to show an open door. It was definitely not required in the US or Canada at that time (and still isn't). I don't recall any '65 literature referring to any such a safety feature, either.

How to reproduce it? Depending on the original material you'd either apply a white paint and then blow glass beads onto the wet paint so they stick to the paint and are retained when it dries, or you'd use retroreflective sheeting (self-adhesive retroreflective material) -- in a 1965 application it would have been what we now know as ASTM Type I or ASTM Type II sheeting.