Robert Roskell began in business in Liverpool in 1805, making chronometers and other horological instruments. The U.S. Navy Bureau of Ships transferred this chronometer to the Smithsonian in 1953. It is a 56 hour instrument with a later pattern Earnshaw spring detent escapement, and indications for hours, minutes, seconds, and up and down. The serial number indicates that it was made in the mid-1850s. In the fractional serial number, the first number is that of the chronometer, while the second is that of all Roskell instruments. Ref: Tony Mercer, Chronometer Makers of the World (Colchester, 1991), p. 231-232.
