Ancient Coins' Modern Usage & Supply

I find it hard to believe that Roman coins were still being used as late as the 18th century. Coinage in Europe was well established in medieval times, that the use of ancient coins as currency was not needed.

The tiniest AE4 coins seem to have circulated at a minimum among the Gothic kingdoms until the reign of Justinian. There seems to have been a deep-seated mistrust of copper coinage throughout most of non-Byzantine Europe, so I imagine that bronzes recovered during the 600-1500 timeframe would have mostly been melted down to make tools etc... it's well documented that most silver and gold recovered during that time (and later) was melted and re-coined

The only instances I have heard of Roman coins re-entering circulation are of the Vandals re-denominating first and second century bronzes as folles or half folles, and of certain coins being over struck in the 17th-19th centuries.

As an interesting aside, I have heard from multiple sources that the Gadhaiya Paisa drachms are still so commonly found in Gujarat that they carry de facto legal tender status in many rural areas; I lost the link, but someone on another forum owned one that was dug up by a farmer and used to buy 2 kilos of bananas.

Bronze coins for the most part have always been token coins used to make change. Unless someone is willing to accept it as such it has little monetary value.
Roman tax collectors in the later empire would not even accept them for payment !
They wanted the good stuff only ....... gold !
Coin finds are for the most part made by people digging in places that have not been explored for centuries. Most ancient cities are located some distance from their modern counterparts. Usually on high ground a safe distance from the sea or river. As modern cities expand outward they often begin to cover ground once used in ancient times and of course the modern metal detectors aid immensely in ferreting out any hidden clay pots buried. The fall of the iron curtain changed things tremendously. Since the 1990's coin hoards have poured out of the Balkans and much of Eastern Europe. Nearly twenty years ago I was buying coins being dumped on ebay by several sellers for "chump change". I have a nice Balkan Sestertius of Nero that I scooped up for $68 !
Those days are mostly gone but the supply continues to grow.
Some coins have actually fallen in price since the early 1990's.
A nice copper as of Caligula set me back $450 in 1992. Today I might get $400 for it. Claudius too is now very common. Not so in 1992.

As far as modern circulation goes I remember reading that travelers to Afghanistan were finding worn Alexander drachms and tetradrachms being used as late as WWI in Central Asia.
Good silver is good silver !
I am sure they weighed everything carefully !

Thanks in no small part to policy and law regarding hoards found in the U.K. being so much less heavyhanded than elsewhere. Most of the material dug up there finds its way into the marketplace instead of being locked away in some museum's vault.