This is an achromatic Officer of the Watch telescope that would have been used on the deck of a ship to make general observations, for instance of signals from other ships. The barrel is covered in leather, while the single draw tube and fittings are made of silvered brass. These include an extending sunshade and a sliding eyepiece cover.

The maker's name is inscribed on the draw tube as ‘Ross / London’, while an additional inscription on the collar of the barrel records that it was owned by Lieutenant A.R. Kerr, RN. Kerr's uniform and swords are also in the National Maritime Museum collections.