Tin or pewter medieval boatswain's call.

The buoy, now flattened, was originally spherical, with ball decoration running along the top. The short triangular keel is formed of pierced lattice-work, with two small rings for attachment to a suspension chain or cord. The gun is straight and decorated with binding.

This early call was found on the foreshore at St Saviours Dock, Southwark. Other examples of medieval whistles of boatswain's call shape can be seen in the Cuming Museum in Southwark, and the Museum of London.

Whistles of this type were used throughout the 16th century to transmit orders on board ships, and became regarded as the badge of the boatswain. Early examples like this may also have been sold as trinkets and have decorative features in common with contemporary pilgrim badges.