Belgian, Flour Bag Seal, Merxem / Merksem Mill, Image & Found by Andy DS.
Found in Hamilton, Scotland, 20mm.
Blank centre, SOCIÉTÉ MOULINS curving downwards, *MERXEM* curving upwards // O
Merxem or Merkem is a town in the Belgian province West-Flanders. The symbol O on the reverse is often found on flour bags normally indicating a grade. Flour used to be categorised into '00', '0', '1' and '2' grades, '00' being the finest and whitest and working down to the almost wholemeal grade '2' flour.
From Michel Royer, "it should read :
"SOCIETE MOULINS * MERXEM *" probably "societe anveroise des moulins de Merxem ("societe moulins" is certain because a similar lead had been presented on exchange-passion, unfortunately there is no longer a photo."