Aluminum tamper keychain charm has a silvery finish.
This tamper, in addition to its finish, is slightly larger than the Gunmetal tamper keychain. The tamper itself stands 1.75" at the top of its dome. The extension that has the keyring in it adds another 1/4 inch to make the whole thing 2" tall.
But just like the Gunmetal tamper, the tamper diameter is the same: 29 millimeters. The inset photo shows their relative sizes.