Micro Seiki - Micromonitor MX-1 Electrostatic Headset

I purchased these prior to 1980 (I think) and have had them in storage for around 25 years. They still work perfectly. I don't have any serious equipment anymore so it seems a shame to have them sitting doing nothing. I remember that they cost £100. ( a lot of money in those days: around 1/2 weeks wages). I may put them on eBay soon.