This is a 56 hour instrument with an early Earnshaw spring detent escapement, and indications for hours, minutes, seconds, and up and down. It dates from the period 1816-1845, before Morris Tobias went into partnership with Isaac Levitt and began trading as Tobias & Levitt. The U.S. Navy Bureau of Ships transferred it to the Smithsonian in 1953. Ref: Tony Mercer, Chronometer Makers of the World> (Colchester, 1991), p. 245.
