Those were my first headphones, bought new in 1974. I got rid of them at some stage. But during a rush of blood to the head, I bought a pair from eBay for not much. The fluid filled earcups were as hard as biscuit, and the foam damping in the cup has turned to tar. Lots of clean up and fabric/foam pads later, I suddenly remembered how god awful uncomfortable they were/are. You head feels as if it being crushed in a vice, and the top of your head is almost bruised by the weight.
I would not have cared so much if the SQ was great. But it isn't either.
How Koss sold these things defeats me.
Koss remanufactured them for a while, but seems that they have stopped.