Amos has a silver-tone devil / demon head pin on his jumpsuit, and a matching tattoo on his arm. I’ve seen many that are close, but none I’m convinced is “the” pin. Retouched screencaps & stills below the jump:
Amos’ pin appears to have a point at the bottom, like a goatee (most obvious in the top right pic). All the Kabuki / Noh demon / oni pins I’ve seen so far generally have a narrow but flat chin.