Austrian, Customs Eagle Seal, Image & Found by Dave Hiddleston.
Found on the Thames foreshore, 15mm.
Crowned eagle displayed with sickle in right talon and hammer in left, shield on its breast // Z.A. / ??EN / 201
The arms are those of the Austria. First used by the First Republic from 1919 to 1934 when Germany invaded and altered it to a two headed eagle without a crown. Then from 1938 it reverted to the original with exception that both talons were shackled but with a broken chain to signify the liberation from the National Socialist dictatorship
Coat of arms of Austria (Wikipedia).
No parallels have yet been found but it looks to be a customs seal.