I believe these were once used on Hercules Aircraft from the 1960's-'70's.

Carry a serial/part number '99-970/30?0' on a cable sleeve.The Cord Mounted isolation switch has the manufacturers name 'AMPLIVOX WEMBLEY-ENGLAND',whilst the earpiece speaker shrouds have the name 'AMPLILITE'.

All in good,untested condition.The rubber jack-plug shroud has signs of perishing,whilst the ear piece removable covers,have ingrained staining. 

A unusual piece of kit from the 'cold war'.

Any questions,please ask.

Will Post WorldwideOverseas by Ebays GSP.

(#My Ref-LT).