I believe the original main cable has been replaced.

Connector is 'B Gauge' / 316 / long frame (these fit but do NOT always work in a 1/4 inch or 6.35mm socket)

This set was tested with MTR HPA headphone amplifier (not in listing) audio heard was good for this style of headphones (better / full range vs others I have listed , The others with reduced frequency response are listed as prop use)

(set #e)