While one can spend thousands of dollars on a popular, beautiful ancient coin, you can also get an interesting coin for under $5.
LRB is a Late Roman Bronze (LRB), I usually think of these as starting with Constantine, or perhaps from Diocletian. I am not aware of a generally agreed start of "Late" - ~4th century AD is how I think of it.
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 two braids, who is reaching backwards.
Barbarous radiates from Gaul are another group that are plentiful and can be found for $5. By my definition this wouldn't be an LRB - pre-Diocletian, pre-4th century.
Despite its ugly, rough, irregular flan, with it's abstract variation on a Tetricus I Antoninianus, blundered legends, brown and rusted patina, line drawing rendition of "PAX" with a right arm that looks more like a cornucopia than a scepter, I like the rugged look of this coin from the northwest territories that were separated from the Roman Empire between 260-274 AD as the Gallic Empire.
Aurelian reunited the empire in AD 274 in a bloody defeat of Tetricus' army in the Battle at Châlons (today Châlons-en-Champagne, France). Tetricus surrendered and survived, perhaps by betraying his army, and later was appointed by Aurelian to the role of governor in Lucania (southern Italy).
A shortage of official coins in the northwest with Aurelian's reform of the monetary system is a leading explanation for why there are so many barbarous coins from this time.