Look at the color of the brass padlock and compare it with the color of the copper prongs at the base of a male electrical plug. Note that the color of brass varies from a dark reddish brown to a light silvery yellow. The color of brass becomes lighter when more zinc is present in the alloy. Compared to copper, brass has a lighter finish. Copper is a light reddish-brown metallic element, and its freshly exposed surface has a reddish-orange color. Copper turns into a shade of green when it starts to corrode.
Hold a piece of copper wire and bend it. Copper is soft and ductile. It can easily be bent and molded into different forms. Brass is stronger and harder than copper. Brass is difficult to bend, and cannot be formed into various shapes without casting or molding it.
Look at the brass padlock and note that brass is used to make various household items, such as pipes, musical instruments, architectural trim pieces, radiators, hardware items and firearm cartridge casings. Copper is mostly used to make electrical wires and other forms of electrical conductors.
Look for the letter "C" markings followed by five digits at the base or other parts of the brass item. In the US, brass items are designated by a Unified Numbering System for metals and alloys.