Small signal cannons were usually meant to fire signals rather than serve as weapons; also called salute cannons, many were used aboard ships and often mounted on swivels, and even a small iron example with a 1-3/4-inch bore would have produced a loud report. This cannon probably dates from the middle to the later part of the 19th century. A small ore car from the famous Utica Mine exemplifies the rugged equipment miners relied on, part of a design that evolved in Europe over hundreds of years from early wooden cars to iron cars on tracks that later inspired large railroad cars. A brass label identifies its maker as Risdon Iron Works of San Francisco, which from the mid-1850s until 1911 supplied mining equipment to the world from its 32-acre factory at Potrero Point. In service, the car would have been loaded with precious ore and pushed by men through narrow tunnels. An arrastra model represents a primitive muller, or ore-grinding mill, used in gold mines to process quartz. Brought to the California Gold Rush by Mexican miners after Europeans had introduced arrastras to the New World much earlier, these devices were often called Mexican rastras or rasters during their period of use. Later improved versions were often powered by water wheels and used multiple drag stones, and the slower but efficient arrastras were sometimes used alongside faster stamp mills to increase gold production.