An electrical connector interface (10A, 10B, 10C, 10D) comprising: a plug connector assembly (20A, 20B) including a plurality of spaced apart conductive contact sockets, each contact socket having a mating end (40, 106) retained in a monolithic mating portion of a nonconductive plug shell body, the nonconductive plug shell body having an external mounting flange (30A, 30B) with a plug anti-rotation aperture having a first non-round anti-rotation portion; a receptacle connector assembly (22A, 22B) including a plurality of spaced apart conductive contact pins extending into a mating portion of a nonconductive receptacle shell body, each conductive contact pin having a mating end configured to engage respective mating ends of the spaced apart plurality of conductive contact sockets, the nonconductive receptacle shell body having an external mounting flange (32A, 32B) with a receptacle anti-rotation aperture; and an anti-rotation fastener post with a first fastener receiving end opposite a second fastener receiving end, and characterized by the receptacle anti-rotation aperture having a second non-round anti-rotation portion; wherein said anti-rotation fastener post is reversible in that, in a first post orientation, the first fastener receiving end is insertable into the receptacle mounting flange (32A, 32B) and, in a second post orientation, the first fastener receiving end is insertable into the plug mounting flange (30A, 30B); wherein the first fastener receiving end includes a non-round external surface insertable into the first non-round anti-rotation portion from an inner mating side of the plug anti-rotation aperture in the second post orientation, and the second non-round anti-rotation portion of the receptacle anti-rotation aperture in the first post orientation. a plug connector assembly (20A, 20B) including a plurality of spaced apart conductive contact sockets, each contact socket having a mating end (40, 106) retained in a monolithic mating portion of a nonconductive plug shell body, the nonconductive plug shell body having an external mounting flange (30A, 30B) with a plug anti-rotation aperture having a first non-round anti-rotation portion; a receptacle connector assembly (22A, 22B) including a plurality of spaced apart conductive contact pins extending into a mating portion of a nonconductive receptacle shell body, each conductive contact pin having a mating end configured to engage respective mating ends of the spaced apart plurality of conductive contact sockets, the nonconductive receptacle shell body having an external mounting flange (32A, 32B) with a receptacle anti-rotation aperture; and an anti-rotation fastener post with a first fastener receiving end opposite a second fastener receiving end, and characterized by the receptacle anti-rotation aperture having a second non-round anti-rotation portion; wherein said anti-rotation fastener post is reversible in that, in a first post orientation, the first fastener receiving end is insertable into the receptacle mounting flange (32A, 32B) and, in a second post orientation, the first fastener receiving end is insertable into the plug mounting flange (30A, 30B); wherein the first fastener receiving end includes a non-round external surface insertable into the first non-round anti-rotation portion from an inner mating side of the plug anti-rotation aperture in the second post orientation, and the second non-round anti-rotation portion of the receptacle anti-rotation aperture in the first post orientation.