While you can spend thousands of dollars on a highly prized ancient coin, you can also get an interesting coin for under $5.
This coin came in a group of uncleaned coins that were about $2/coin. It is a Fel Temp - happy times - type of Constans or Constantius? At 2.9g is a favorite of mine for because of it's detail carved by an ancient engraver, the strike and design on both the obverse and reverse - unusually high relief. The jagged edges of the coin reinforce the drama and violence of the reverse design.
Constantius II (?), AE
Obv: D N CONSTANTIVS P F AVG, pearl-diademed, draped and cuirassed bust right
Rev: FEL TEMP REPARATIO, soldier standing left, spearing bearded horseman, hair in braids.