This is a reproduction of a silver denarius of the emperor Trajan. This denarius was struck at Rome in AD 98-99. Precise dating is possible on account of the reverse legend which shows his second period of holding office as Consul (COSII).
The reverse shows Pax standing left holding an olive branch and cornucopia. The type is listed as RIC 6 and RSC 209 but is not listed in either the new or old editions of Sears Roman Coins and Their Values.