Enamel pins are usually made of copper, iron, zinc alloy, etc. Popular pins sizes between 0.5-3.0 inches. On the front side, there are recessed area filled with colorized paint.
Based on process, there are hard enamel pins, soft enamel pins, die-struck pins, offset print pins,etc.
To ensure good looking and prevent rust, enamel pins are often plated with gold, silver, nick, black nickel,etc. Some pins are coated with a transparent protective resin (epoxy). For some designs, they are too detailed to be able to use paint, then screen printings are carried out on the pins.
On the back of pins, logo is often stamped to identify its publisher or orginazation. Branding building or awareness is one important purpose of enamel pins issuing.