I bought it on Ebay for $ 24. This is a clone of Rystl Electro-3000 & Alarik CIS-3000 and Yes they are electrostatic (electret). I can tell one thing from the sound: it's very soft! This is the first time I've seen this..
Wow, interesting find! Have any more impressions of them coming up? I've been looking into vintage headphones lately and came across the Rystl a few times, but haven't been able to find many details about how they sound.
I don't even know how to describe their sound exactly. Electrostatic headphones have always had a very detailed sound. There is definitely no such sound here. It's like listening through cotton wool! But the construction itself is very convenient. My head doesn't get tired. I don't know why, but I still like the sound. Apparently it is not ordinary... I just have a lot of vintage headphones of various types. So I want something special..