Some 67 Barracudas with deluxe interior package could have had chrome seat adjust knobs. I think all of them were chrome before 67. I'm not sure though. Mine came from 66 bucket rails that were deluxe interior.
These earlier knobs had a simple knurl nose allen set screw. The later knobs had a pin point set screw. That pin would often be so distorted in the hole through the arm that we cant back the screw out to remove reuse the knob