Cloth Seal, Cloth Worker's Personal Seal, Privy Mark, SPM?

Cloth Seal, Cloth Worker's Personal Seal, Privy Mark, SPM?, Image and Found by Puffin.
Found South East Staffordshire on the border with Warwickshire, 20mm?.

Part of a privy mark incorporating S (P or B) and possibly M // missing (traces of a letter stamped on the rivet stub)

An unusual rivet disc from a two-disc cloth seal with a ridge around the reverse edge.