Corbeau's screencaps come from
Abigail Lesley is Back in Town (1975, Joe Sarno, dir.) which is softcore btw.
Mary did mostly softcore, but a little hardcore as well. I have an uncut copy of
The Image, in which she screws Carl Parker during the B&D scene -- definitely not faked. That is one of the most erotic films ever made, despite the fact that the actual sex scenes are few and brief. Some consider it Radley Metzger's best film, although others argue for The Opening of Misty Beethoven (which Metzger directed as "Henry Paris").
Two other Mary Mendum films worth seeing, besides those already mentioned, are
Laura's Toys and
Confessions of a Young American Housewife, both soft (although
Confessions can be found with hardcore inserts).
Edit: English softcore version is posted
here.