The gentleman's and trader's guide. [electronic resource] : Containing, the description and use of a new-invented instrument, for preventing frauds by counterfeit gold, which Gives the Weight, and shews the Alloy of that metal, as well in Coin as in Rings, Jewels, and all Kind of Utensils made thereof; with The Quantity of Adulteration (if any) The instrument Is neatly made in Brass, and very easily portable in the Pocket - Any Person, by sending to the authors, (post paid) may have an Instrument made to Weigh and prove any larger Coin or Utensils of Gold and Silver than This Instrument is design'd for, By W. Bradford, Teacher of the Mathematicks, R. Darby, and J. Hulls. All of Campden, in the County of Gloucester. Sold Wholesale and Retail by the Patentees at their Ware-House in Campden, and in most Towns in England.