Assuming the door windows have not been changed from original, those quarter-lights were designed to open. However, over the passage of time (and perhaps several owners) they might have been glued shut, the catches may have seized or the pivots broken so sealed shut.
On my '72 164E my 1/4 lights whistle in the wind when driving (!) because the catches came off (they were glued to the glass in those days, and the glue failed) but I can live with that. However, I have more than one (!) pre-1971 164 too (suppose I'm a hoarder!) and they all have differing catches. Possibly some were deviations from what was originally fitted for some reason, possibly there were different options then?
I can photograph my differing types for you if interested, but can't post here: mail me on
paultill38@gmail.com so I can send direct. Won't be instant though as grand kids off school so full-on entertainment season!
P