You might like this old thread: In a recent TIL, it's said that the "Roman Empire" lasted about 2,200 years. Was currency transferable during that whole time? If I was to, say, have a Roman coin from 500BC, would it still have the same value in 1000AD, or would it be treated as a more valuable piece of history?, in particular a good post by /u/Porphyrius .

Using old coins could certainly raise curiosity, if not outright suspicion. The story Seven Sleepers of Ephesus dates back to circa 500 CE. In it, seven Christians during the reign of pagan Emperor Decius are persecuted. They flee into the wilderness and fall asleep in a cave, waking up several hundred years later when Christianity was widespread. One of their number goes into Ephesus to buy food and astonishes the merchants when he tries to pay with a coin from the reign of Decius. As Gregory of Tours describes it:

But when they saw the silver coins, they said: “This man has found an ancient treasure trove; and he’s got silver from Decius’ times!” As Malchus heard this, he turned thoughts about in his heart, saying, “What do they covet these old things for? Is it possible I’m watching a dream?” But some men grabbed him and led to the bishop Marinus and to the city’s Prefect of police. He said to him: “Where are you from; or what area have you come from?” He said, “From Ephesus: But isn’t this city the Ephesians’ which I recall I saw yesterday?” “The silver coins you hold,” said the Prefect: “Where did you get them?” He replied, “I got them from my father’s home.” The Prefect said: “And where’s your father?” and he named his parents, but none recognized. The Prefect said “Tell us where you got these pieces of silver: They are from Decius’ time, and he is dead for many years. Clearly from somewhere, since you have come to trick the wisemen of Ephesus, and so will you suffer under torture until you disclose the truth.”

The readers or listeners of the Seven Sleepers story would have understood that using 200 year old coins would be so unusual to attract attention. That doesn't mean they wouldn't be accepted, however.