Interesting evidence suggesting that the last date of a coin in a hoard might not be that suggestive of the date the hoard was buried. Although the date of the latest coin is most certainly the terminus post quem, nonetheless the actual dating of the hoard burial might be even a century later, as indicated in this instance by other evidence; a third century coin hoard cut into fourth century archaeology.

News: How do you date a hoard? The case of Bredon Hill : Current Archaeology:

A two-week excavation by Worcestershire County Council Historic Environment and Archaeology Service then opened a small trench over the find spot which revealed that, unusually, the hoard had been buried in the ruins of a late 2nd-3rd century Roman villa. Furthermore, while the coins ranged in date from AD 244-282, they lay in a pit cutting through a layer of soil containing 4th-century pottery and a coin dating to c.AD 355-361. This suggests the hoard may have been buried as much as a century after the minting of the latest coin.

(Via Current Archaeology.)