I am listening to a pair as I type this. I got them in '73 making them about 36 years old and they still sound great. I've used them all these years and am now just looking for a new pair to replace them. I imagine cans have improved over the years.
They retailed for about $80 new which is about $450 today so they were a high end option in their day. I'll type the specs from the sheet:
Speakers: Polyester cone - 1/34 inch
Impedance: 8 ohms
Matching Impedance: 4-16 ohms
Freq response: 20-20k Khz
Sound pressure level: 113dB
Maximum Input: 500mW/channel
Cord Length: 16 feet, coiled
Weight: 1 lb 1 oz
Volume controls are wire-wound and are a little scratchy but not an issue if you don't overly mess with them.
I've loved them all these years and will hang on to them. They are relatively heavy but I can wear them for hours without a problem. I can't even remember how good they should sound...been running them through an old Aiwa 40 watt shelf system that butchers the sound. The source is a hard drive running through a 5 year old entry level sound card with a 1/8" out that connects to a cord that splits into two RCA jacks. So, given the situation, they sound very good. I plan on getting a NAD integrated amp and substantially upgrading the sound card and cables soon so I'll see if they still have what it takes.