Danish, Statens Plantetilsyn Seal, Image & Found by Phil Philly B Brenkley.
Found in Durham, 18mm.
Danish crown // STATENS / PLANTE / TILSYN
From Steen Agersø, "Statens Plantetilsyn, institution established 1914, with the purpose to control exports of fruit and vegetables for plant diseases and pests.
This means that the product (agricultural) has been checked in Denmark, before the export to England. ... I would guess that the seal is from the 60s till 1990, as I think they used lead before that?"