Not to start an arms race, but that second picture I posted has Mueller coppers in the forefront then Western KS series, made by Mueller and nickel plated brass. They're doing "finalized" duty on tweeter caps.You guys better all hurry and switch to the copper non-magnetic clip leads before you are stripped of your audiophile credentials, you'll no longer be card carrying, the cops are coming.
If you're chasing purity, though I know your comment is tongue-in-cheek, I'd be suspicious of those Amazon sourced ones. Not all copper is what it seems.