[2] In 1856, United States Secretary of the Treasury James Guthrie appointed Preston to a clerkship in the office of the first auditor.

[2] He rose through the ranks in that office and was responsible for auditing the accounts of the United States Mint.

[4] Preston served as Computer of Bullion, Assay Clerk, Adjuster of Accounts, and Mint Examiner.

[4] At several times, he served as Acting Director of the United States Mint in the absence of Linderman and his successors, Horatio C. Burchard and James P.

[5] Preston held office from November 1893 until February 1898, after which he reentered the Mint Service as an Examiner.