That's a denarius of Trajan - predecessor of Hadrian (who built a wall up your way - you might have heard of it...) - under whose reign from 98-117 AD. the Roman Empire attained its largest size (briefly, before Hadrian gave Parthia back to the Parthians).
The reverse reads 'S.P.Q.R. OPTIMO PRINCIPI" - a standard reverse legend paired with dozens of reverse types. This one seems to be Mars advancing right. This series dates to about 107 AD. and the obverse legend in its entirety most likely reads IMP TRAIANO AVG GER DAC P M TR P COS V P P.