I ran into this interesting little tidbit that appeared originally in the Oct. 16, 1873 issue of the Philadelphia North American, while doing some research. Apparently the introduction of the new Trade dollar, which had been authorized earlier that year by the Coinage Act of 1873, warranted the building of a new, more powerful press for use at the San Francisco Mint:
We were shown yesterday at the works of Messrs. Morgan & Orr, No. 1219, Callowhill Street, the new coining press, just built by them for the purpose of coining at the San Francisco Mint all denominations of silver and gold coiange, but especially the new silver trade dollar ordered by the Department of the Mint.
This new machine weighs eighteen thousand pounds, and is made entirely of the best steel, iron, and brass produced in Philadelphia. The steel plate above the coinage stamp is home-made, and equal, if not superior, to the finest English, a fact that speaks well for our Philadelphia steel industry. The beautiful heavy brass beam was cast seven times over to secure its accuracy and exactness, as well as finish and strength. The large fly-wheel is cast hollow, and loaded with base metal so as to give it additional weight to counterbalance the heavy brass beam. This fly-wheel was cast in sections and securely united. In the front of the machine is a finely made brass cylinder to hold the unstamped coin, which as the wheel revolves, slip down one at a time upon the sliding bed-plate of iron with apertures made to receive a single coin, then drawn into the machine, the stamp descends, and the new trade dollar is carried out complete by an interior inclined plane. The heavy brass beam referred to of course controls the stamp. Perfect simplicity characterizes the machine, which is two and a half times beyond the capacity of any other coining machine that the firm ever made for the government. It is capable of striking eight twenty-dollar gold pieces, equal to $1,600, per minute, or twenty silver trade dollars in a minute.