this coin was recently auctioned in Naville 33. The reverse has three Monetae, which represent the mints for bronze, silver and gold coinage. There is speculation that this type was issued either because of improvements to the mint or coinage reform.
Valentinian I, 364-375 at Rome circa 367-375, 28.5mm., 7.15g. Diademed and draped bust r. Rev. The three Monetae standing facing, head l., each holding scale and cornucopia. C 14 (40 Fr.) RIC 19a.