This 'vacuum' chronometer is attributed to Joseph Manton, the London gunmaker, who in the closing years of the 18th and early years of the 19th Century experimented with air-tight cases for chronometers (R.T. Gould, The Marine Chronometer, 1923, pp. 228-229). In January 1808 Joseph Manton was granted Patent No. 3085, the specification of which includes the statement 'I, the said Joseph Manton, do hereby declare that my said Inventions in Timekeepers consists of an instrument or machine for timekeepers to act in vacuum, so constructed that they may be wound up in vacuum when required without admitting the external air, as is hereafter described in the explanation of the annexed Drawing.' Manton is known to have made two 'in vacuo' chronometers. The other is now in the collection of The Museum of Victoria, Melbourne, Australia and its dial is signed Joseph Manton and has the identification 'M' within the seconds dial. The construction of the movement is, with the exception of the octagonal-shaped stuffing box, almost identical to this chronometer, suggesting the attribution of the present chronometer to Manton.
Between December 1808 and February 1809, by prior agreement with the Board of Longitude, Manton was permitted to deposit one of his 'in vacuo' chronometers with the Astronomer Royal at Greenwich Observatory. He was subsequently called before the Board and in answer to the question 'Who was your watch made by?', replied 'By Mr Pennington'. See K. Neal and D.H.L. Black (The Mantons, Gunmakers, London, 1967, pp. 148-153).