G.P.O. Seal, HAM, Image by StuE, Found by Goretex.
Found in ?, 17.8 x 18.3mm, 8.8g.
Typical square, tubular, deeply crimped seal used by the General Post Office for sealing letter sacks.
This one has HAM G.P.O.2 along the bottom of one side and RO(T?)HE(R?) along the top - ROTHERHAM maybe.