Double-breasted frock coat of superfine blue wool belonging to Commodore Henry Caldwell, Commodore 2nd Class. The collar and lapels are shaped by rows of running stitch. Two miniature medal ribbons are stitched onto the lapel, the upper one of pale yellow edged with pale blue is for the Crimea while the larger, lower ribbon is of crimson silk and is for the Order of the Bath (Caldwell was a Companion of the Bath).

The coat fastens with two rows of eight gilt brass buttons of the following pattern: domed button with rope twist outer edge, raised inner border, anchor and crown on lined ground. The shoulders are gathered and padded and the cuff is edged with a broad stripe of distinction lace. The top edge of the lace features the distinctive 'curl' introduced into Royal Naval uniform in 1856.

The 'single stripe of broad lace (1 ¾ inch) on the cuff' for a Commodore 2nd Class makes its first appearance in the 1863 Regulations. However, these did not mention whether or not the curl should be included. This was rectified the following year.

The skirts and back of the coat are lined with black silk twill and the underarms have additional wadding stitched into the lining. There is an interior breast pocket. The arms are lined with white cotton and have a black silk lining at the cuff. The back features both hip and pleat buttons.

The frock coat, which comes directly from contemporary fashion of the 1840s, was introduced into the Royal Navy in regulations in November 1847. It was called a 'Surtout Frock Coat' and, with the exception of Flag Officers, it was not worn with epaulettes. Rank was shown through distinction lace on sleeves. The frock coat was worn until 1949.