The merchant's magazine; or Factor's guide. [electronic resource] : Containing, great variety of plain and easy tables for the speedy casting up of all sorts of merchandize, sold either by number, weight, or measure; and for reducing sterling money into currency at sundry rates; with tables of interest and rebate, and of the value of gold and silver in Virginia: also tables shewing the amount of any quantity of goods at almost any per cent. advance on the prime cost, and for finding the nett duties on tobacco from one pound to fifty thousand pounds. To which is added, some tables of per cents. on transfer notes, the whole applied throughout to trade and merchandize. By Robert Biscoe, of Lancaster County.