This is a coin of the Emperor Septimius Severus 193-211 AD. Obverse legend is SEVERVS PIVS AVG and the reverse legend is PM TR P XVI COS III PP. Jupiter standing aiming a thunderbolt and holding a spear. Nice coin.
It is indeed silver; it's a denarius. The specific type isn't listed in the Sear catalogue, but denarii of Septimus Severus typically go for around $40 in VF condition. The patch of green goo on the reverse of your coin might lower the price, if it's corrosion rather than just uncleaned patina.
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