Colin Smith said this coin has been in his collection for many years but it was his first hammered silver find. I was asked to provide further details.
The coin is a voided short cross penny. Coins of this type started to be struck during the reign of Henry II and they continued to be issued until the long cross type was introduced in in 1247, when Henry III was on the throne.
On the reverse of this coin the legend reads +ROBERD ON CAN, so Roberd is the moneyer and Canterbury the mint. It was struck during the time that class 4 was issued under Richard I but I can’t pin it down to a definite sub-class as the obverse is double struck and this obscures some of the detail.
As just mentioned, the obverse is double struck and would grade only about Fine. The reverse is much better and this side would grade good Fine. In its present state of preservation I’d price Colin’s find at £40.