1965 brochure

[dubtrub]

Close call, but that is not a third knob on that double neck. It looks like it, but that is a black tipped selector switch. The tip of the flip mute protrudes within a 1/4 of an inch of the switch tip casting the elusion that it is a third knob. That is an interesting arrangement of knobs and switch position on the inset photo, but that is a close-up of the single neck.