This is interesting. The cross in quatrefoil appears to read AELFGAET ON BRI. Aelfgaet is recorded as a moneyer at Dorchester for W2 types 2 (this one) and 4 (cross pattee & fleury). The reading of BRI is ambiguous as it could be either Bridport or Bristol. Bridport isn't currently known for William 2, so this would extend the life of the mint by a few years. A coin of Aelfgaet reading BRIC would positively place the moneyer at Bristol, but for the time being the jury is out. Either way it is possibly unique unless someone can state otherwise.
Given the presence of Aelfgaet at Dorchester, Bridport seems the more likely, and it is quite a rare mint to boot. It isn't a piece of beauty, but well worth having.