These limited key tags are wire EDM cut from naval brass and Cupro by our friends at HogDoggins. Aside from the collectability, the tactile feel and unique shape are good fidget/worry tools.
Cupronickel: Despite its high copper content, cupronickel is silver in color. Cupronickel is highly resistant to corrosion by salt water, and is therefore used for piping, heat exchangers and condensers in seawater systems, as well as for marine hardware. It is sometimes used for the propellers, propeller shafts, and hulls of high-quality boats. Other uses include military equipment and chemical, petrochemical, and electrical industries.