The 1806 6 over Inverted 6 Half Dollar is one of the more interesting "overdates" in the series. When creating the die, the engraver punched the 6 of the date upside-down, which was clearly a mistake since his 1809 die was three years early. He corrected the mistake by re-orienting the 6 correctly, then giving it a good punch to cover up the underlying 6. However, such efforts are usually futile, as remnants of the underdate are almost impossible to cover up. It does not appear that any attempt was made to efface the mistake, thus modern collectors have an unusual variey to add to their collection.
The 6 over Inverted 6 was paired with two different reverse dies, creating the Overton 111 and Overton 112 varieties. Both are of approximately the same rarity and both are very scarce. High-grade examples are very rare and we know of only four Mint State examples. The best is the PCGS MS64 from the Norweb Collection, which resold in 2015 for a record $82,250.