historicalfashion:

Military jacket, British | Met Museum | c. 1862

The initials on the epaulettes of this naval jacket stand for Medical Service. The title was replaced in 1872 with M.D. (Medical Department). The length on the epaulettes distinguishes rank, in this case the 2.5-inch length indicates the rank of assistant surgeon. It was worn by Leonard C. McPhail in about 1862.