Mounting positions for exterior mirrors that were fitted to old Volvos are like snowflakes, no two are alike. The mirrors were installed at the dealerships rather than at the factory and we've seen a wide variance in their placement (often they've been installed so the wing window won't open fully).
The orignal mirrors used threaded studs that protrude into the door so the mounting hardware wasn't visible (or accessible) from outside the car. The current reproductions instead use screws, which can been seen, but the mirror body and base are virtually identical in styling. The function just like the originals and can be installed in about 10 minutes.