352-355 AD., Constantius Gallus, Aquileia mint, Æ2, RIC 196.

Constantius Gallus, Aquileia mint, second officina, 352-355 AD.,
Æ2 (18-20 mm / 4,02 g),
Obv.: DN CONSTANTIVS IVN NOB C, bare-headed, draped, cuirassed bust of Constantius Gallus right, A behind bust.
Rev.: FEL TEMP RE-PARATIO / [A]QS , soldier spearing fallen horseman who is bare-headed, reaching backwards; LXXII in left field; chi-rho-monogram in centre.
RIC VIII, p. 333, no. 196 (C) ; Paolucci & Zub 582 (R) ; LRBC 927 ; 5 pieces on http://www.nummus-bible-database.com, only 1 from officina 2 .

LXXII for made of 1/72 of the Roman pound (326 g,) , ca. 4,5 – 4.7 g.

More on https://en.wikipedia.org/wiki/Ancient_Roman_units_of_measurement