Denarius, type 3

Obverse

Obverse legend

Reverse legend

Reverse

Rx P (the letters R, x and P under a tilde).

SCI MARTINI (circular legend counterclockwise (degenerate? some retrograde letters) around the letter S itself surrounded by dots, the letters N and I mixed; the letters S, C and I separated from the letters M, A, R, T, I, N and I by a cross). 

Photo of a coin sold by cgb.fr, link to the sale and their website: https://www.cgb.fr/pepin-ier-dit-le-bref-denier-ttb-tb-,bca_344191,a.html.

The reverse legend is probably SCI MARTINI and not MARTIN as often noted by auction houses, indeed the letter N and the letter I are in monogram, often difficult to dissociate. A vairant exist with the legend MARTI, classified on this website.