John Fothergill entered into partnership with Matthew Boulton in 1762 and their Soho manufactory, a model of its kind, was housed in its new Palladian building by 1765. In the five years following, the capacity for producing larger silver wares and not merely toys (i.e. buckles and buttons) increased and from the late 1760s a handful of objects survive made by Boulton and Fotherfill in their Birmingham factory and hallmarked at Chester, the nearest assay office. In August 1771 Boulton was writing to the Duke of Grafton to apologize for a cup that had been "delay'd and mark'd, which is a grievance that will prevent us (unless removed) from ever establishing an extensive Manufactor of Silverwares upon such a footing as will be most advantageous to this Kingdom."

By incessant lobbying and by joining forces with the silversmiths of Sheffield, in a similar predicament, at last Royal assent was received for a bill setting up assay offices in the two towns on May 28, 1773. It is said that as the lobbyists from the North had done so much of their negotiating at the Crown and Anchor tavern in the Strand, it was there that they tossed a coin to decide what their town hallmarks should be; Sheffield won and got the crown, while Birmingham had to content itself with the anchor. The Birmingham assay office opened August 31, 1773 with Boulton and Fothergill among the first of its customers. This cream jug is among the first objects assayed and marked by the Birmingham assay office. (Kenneth Crisp Jones, ed., The Silversmiths of Birmingham and Their Marks 1750-1980, 1981, pp.27-29).