Engineer-in-chief of the Navy during the Civil War (1822–1915) he helped to found the Navy's Bureau of Steam Engineering. Ink signature, “Chief Engineer B. F. Isherwood, Chief Bureau Steam Engineering, Navy Department,” on an off-white 5.25 x 2 lightly-lined slip. In fine condition, with some scattered light toning. Accompanied by an unsigned cabinet portrait of Isherwood and his staff. RR Auction COA.
