This coin looks massive but it’s a hammered silver halfpenny and is only about 15mm in diameter. It was unearthed by Glyn Peak, who had identified it as a London coin of Edward II.
On the obverse the legend reads +EDWARDVS REX AN, so it does match number 1472 in the Standard Catalogue. It is listed as class 10-11 and placed under the reign of Edward II. However, it is indistinguishable from halfpennies struck during the first coinage of Edward III, which are listed in the Standard Catalogue as number 1536. Therefore, we have the same coin in the catalogue for two different reigns.
As Glyn’s find would grade Fair to Fine and as it could not be said to be common I’d price it at £30.