Post Office GPO Seal, Image by StuE, Found by Allsopp.
Found in the Staffs area.
Standard General Post Office square bag seal with BHAM on one side and RESERVE on the other.
In 1911 the post office replaced wax seals used in smaller post office regions with lead ones for sealing letter and parcel sacks (lead seals were used in the the larger post offices probably since Charles I opened up his royal mail to the public in 1635, Oliver Cromwell established the General Post Office in 1657). In 1916 they made the seals thinner reducing the amount of lead by 19% thus saving £1,770 per annum. The Post Office Controller of Stores supplied the lead to the seal manufacturers directly. These manufacturers at the time were, Dunham White & Co Ltd., J.N.Lyons Ltd., The Lead Seal Manufacturing Co. and Walkens, Parker & Co. Ltd.
(This information was gathered from The British Postal Museum & Archive, Freeling House, Pheonix Place, London.