He undertook several duties for the museum, not least as a witness in criminal trials, but was primarily their specialist restorer, perhaps the first person to hold the position.

Yet the accuracy he achieved led to confusion with the originals; after his death he was labelled a forger, but with the caveat that "[w]hether he did copies with the intention of deceiving collectors or not is open to doubt".

An obituary noted that he worked at a printer's shop for more than 20 years during his youth, which gave him the experience of casting type that he would employ in his later career as a copyist.

[14] At his death, it was noted that he was "chiefly employed in the reparation of innumerable works of art, which could not have been intrusted to more skilful or more patient hands",[2] and that he "was well known as one of the most valuable servants of that department".

[17] Only 37 small splinters, most from the interior or thickness of the vase, were left out; the cameo base disc, which was found to be a modern replacement, was set aside for separate display.

[21][22] A new base disc of plain glass, with a polished exterior and matte interior, was diamond-engraved "Broke Feby 7th 1845 Restored Sept 10th 1845 By John Doubleday".

[4] In 1851 he successfully undid damaging restoration work by William Thomas Brande of the Royal Mint, who in using acid to clean bronze bowls from Nimrud had caused extreme oxidation.

[32] Doubleday's method, described at the time only as "a very simple process and without employing acids", is unknown, but may have used warm water with soap.

[34] Under the direction of Samuel Birch, then the keeper of the Department of Oriental Antiquities, Doubleday attempted to remove the deposits.

[35] The results were described by E. A. Wallis Budge, former keeper of Egyptian and Assyrian antiquities at the museum, as "disastrous",[36] but by modern reasoning as "prescient", for though unsuccessful, the underlying methods were subsequently refined by others.

[44][49] Doubleday was called to testify on Thursday or Friday; he stated that some of the coins exactly matched sulphur casts which he had made before the theft, and that the market value was between £3,000 and £4,000.

[54] Vlasto was sentenced by the Central Criminal Court to seven years transportation to Australia,[46][55][56] and in early 1851 was placed on board the Lady Kennaway for the journey.

[2] He sold sulphur and white metal casts, the former coloured in different hues, at his establishment,[58] which, located near the British Museum, may have helped facilitate his employment there.

[58][79] He was well known among collectors,[80][81][82] and also sold to lyceums; University College London filled out their collection with his casts, finding them cost-effective substitutes for study.

[83][84] Doubleday was cast as a forger in Leonard Forrer's 1904 Biographical Dictionary of Medallists, though with the caveat that "[w]hether he did copies with the intention of deceiving collectors or not is open to doubt".

[25] An 1859 edition of The English Cyclopædia described him as American,[86][note 6] and the 1851 census as a New York-born "artist" who was nonetheless a British subject, married to one Elizabeth and father of five daughters,[4] all Londoners.

[4] Doubleday worked at a printer's shop in his youth for more than 20 years, according to his obituary in The Athenæum, giving him experience through making type in the casting of metal and other materials.