Guano Seal, Biphosphated Guano Co, Image by StuE, Found by Simon Col Club.
Found in Colchester area.
Written around the outside of one side is BIPHOSPH[ATE GUANO Co] with LONDON at the bottom [the letters inside the square brackets are interpreted]. Across the middle is written LIMITED. The other side has a bird in flight with TRADE above and MARK below.
Board of Trade and successors: Marine Maps and Pla... BT 356/10020
RIVER THAMES, BLACKWELL POINT; PROPOSED CONSTRUCTION OF LANDING STAGE BY BIPHOSPHATES GUANO COMPANY; assent granted; related to H634, 1 maps . RIVER THAMES, BLACKWELL POINT; PROPOSED CONSTRUCTION OF LANDING STAGE BY BIPHOSPHATES GUANO COMPANY; assent Date: 1879 Source: The Catalogue of The National Archives