Robert Bartlett, professor of Medieval History at the University of St Andrews, has written that the success of Henry II's short cross type coinage issued in 1180
was so great that no one was willing even to tamper with its
inscription, so that English pennies bore the legend 'King Henry'
throughout the reigns of Richard I and John.
Source: Robert ...
I don't know why Richard or John wouldn't get around to changing the name on the coins, especially if they did change the dates on the coins. And if they didn't change the dates on the coins, how do coin experts know there are coins from the reigns of Richard and John with the name of Henry?
One sort of analogous situation is the continued minting of ...