Are you sure Steve? The Auburn hooks used on the earliest were short shanked and the yellowing on the plug's varnish should be matched with the tarnishing of the brass thru wire and hook hangers. Even if the plug was always kept in the box a subtle electrolysis would set up between the tin/cadmium plating on the hooks and the brass which usually led to a white powdery coating of the hooks. I see a little rust. Hmm that's interesting.
