Merchandise and other necessary supplies kept on hand in order to do business.
1848, Charles Dickens, ,The stock-in-trade of this old gentleman comprised chronometers, barometers, telescopes, compasses, charts, maps, sextants, quadrants, and specimens of every kind of instrument used in the working of a ship's course, or the keeping of a ship's reckoning, or the prosecuting of a ship's discoveries.
A technique, skill or ability habitually used by a person, group of persons, or an organization, often in the course of their business.
1890, Nellie Bly, ,Ideas are the chief stock-in-trade of newspaper writers and generally they are the scarcest stock in market, but they do come occasionally