Cloth Seal, London Dyers Company, Image & Found by London Mudlark.
Found on the Thames foreshore, 22mm.
Shield bearing on a bend three ducks // W.. above a madderbag
There are several families who use three birds on a bend as their family arms. Reade and Portington are possibilities, "Gu. on a bend arg. three shovelers sa. Reade, co. Lincoln. But three teals sa. Portington." from An Alphabetical Dictionary of Coats of Arms Belonging to Families in Great Britain & Ireland, Papworth & Morant 1874.
The madderbag suggests a connection to the London Dyers Company. The W above usually indicates woad has been applied. See p.92 & Nos.270 & 271 Fig.35, Geoff Egan, Lead cloth seals and related items in the B.M. (B.M.occ.papers 93).