Three sisters from the Toledo, Ohio area inherited the “error” coin after the death of their brother, who, along with their mother, purchased the dime in 1978 for $18,200 (estimated to be $90,000 today) . They discovered the dime in their bank vault and it has now sold for over half a million dollars.

The dime depicting former President Franklin D. Roosevelt is missing the “S” mark from San Francisco, where it was minted in 1975. It is one of only two known coins without the “S” mark, making makes it especially valuable.

The sisters, who wish to remain anonymous, said their mother and brother bought the currency because they considered it a financial safety net. The coin sold this week for $506,250 in an online auction held by Great collections with more than 200 offers.

The other rare 1975 dime sold for $456,000 at a 2019 auction before being given to another collector. The whereabouts of these two “error” coins had been a mystery since the late 1970s until one of them turned up between the sisters, The Enquirer reported.