This is the only one of the three marine chronometers owned by the museum to be recorded in the inventory of 1873.
The quadrant bears the words Parkinson & Frodsham / Change Alley London / 3723 and shows the insignia of the English sovereign and coat-of-arms with anchor with the words Exhibition 1851. The trademarks Parkinson & Frodsham and Change Alley London are also engraved on the back.
It has gimbal suspension, Earnshaw-type escapement and wound up lasts for 48 hours.
Charles Frodsham produced a large number of instruments both with his name alone and in partnership with Parkinson and Keen in Liverpool. The number 3723 engraved on the quadrant allows us to hang a date on it, in that it comes shortly after the 3688 of the analogous chronometer at the Greenwich Observatory, dated around 1840.
In a letter of December 12, 1870, the then director of the Specola, Jacopo Michez, in response to a request from the Central Telegraph Office "to establish, by means of an appropriate electrical circuit, communication between a regulator clock of the said Observatory and another clock of the Telegraph Offices in Bologna", points out that "the Observatory possesses an excellent chronometer by Parkinson and a few equally good cycloidal clocks; by means of astronomical observations it was possible to frequently measure the accuracy of these clocks, then regularly recorded in registers" (Arch. Dip. Astron. Bo., letter-book 1865-1873, p. 199).
Just before 1906 it was repaired - as recorded in Rajna (op. cit.) - "by Mr. Milani, skillful watch-maker and machinist at the Observatory of Brera in Milan." In 1992 it was restored by Leano Colliva of Bologna.
T.N. Clarke, A.D. Morrison-Low, A.D.C. Simpson (1989), pp. 141, 237 and 242.
An Inventory of the Navigation and Astronomy collections in the National Maritime Museum Greenwich (1970-73).
M. Rajna (1906), p.27.