Veteran pornographer Claude Bernard-Aubert, who uses the nom de film "Burd Tranbaree" (an anagram), puts his talent through familiar motions in "Private Secretaries Service". It has been recently reissued in an Alpha France series on DVD from fetish label Third World Media.
The packaging lists Feb. 24, 1983 as its Paris debut date, likely fictitious as IMDb agrees with the 1980 copyright on screen. It's basically a "who's doing whom" movie of sexual musical chairs.
The boss is serviced by his secretary Joanne, who sends him off at the end of workday to a distant meeting so that she can hook up with his wife. Both she and wifey have sex in threesome with brunette house maid Mary, and similar round-robins abound involving sisters plus the boss, thanks to sort of walkie talkie hook-ups, being pretty much aware of all the shenanigans going on.
There's a subplot involving a gold oversized dildo that they're marketing but other than finding out if the head will fit in respective femmes' vaginas, it's not all that relevant to the story. The fault of French films of this period, and this one in particular, is that the sex is highly professional but (especially dubbed into English) the acting is impersonal. Also, Claude did not employ any raving beauties this time out.