ARNOLD No.511 first appears in the Royal Observatory Chronometer Ledger (pp.58,65) 29 August 1822, when it was issued to the brig-sloop
HMS Pandora at Plymouth. Between 31 Aug 1894 and 5 April 1904 it was in use in HMS Britannia, the naval cadet training ship which was later to become Royal Naval College Dartmouth (RG05/238 and Greenwich Observatory Chronometer Indexes)
In 1879 Arnold No.511 was modified by William Crisp, a Government chronometer repairer, without the Astronomer Royal's permission. His modification was to recess the engraved enamel disc graduated in degrees into the surface of the top-plate beneath the balance to assist accurate observation and measurement of the balance's amplitude. This led to contentious correspondence, the Astronomer Royal refusing to pay Crisp for unauthorised work (RG06/606 529-556). This assembly is no longer in situ and it seems probable that Crisp removed it before returning No.511 to the Royal Observatory in August 1882. On 29 August 1911 it was sold to Usher & Cole.
Included are copies of certain relevant RGO correspondence dated variously from 1822 to 1911.