Rotterdam Thomas? & Son Seal, Image & Found by Pete Senior.
Found in Portrush co.Antrim.
Arms of Zealand // THO(M?)... & SON outer circle ROTTERDAM inner circle
One side has a shield baring a rampant lion with three wavy bands covering the lower half. This is the arms of Zealand, A lion rampant emerging from the sea. The other side has two lines of writing curved one inside the other. The middle word is ROTTERDAM, the outer is largely missing but either end can be made out THO(M?)------ then & SON. Thomas is a guess but there seems to be space for a longer word? Rotterdam is situated just north of Zeeland in the province of South Holland.