Koss HV/1A found in an old basement, replaced the cushions, sound great w/ some EQing! : r/headphones
1973 Koss HV1 Stereophone: Only the Sound Is Heavy Vintage Print Ad | eBay
Shop Koss High Velocity HV 1 A & Discover Community Reviews at Drop
Vintage Koss HV/2a's opened up!!! PICS!! + Need help w/ repairs. | Headphone Reviews and Discussion - Head-Fi.org
Amazon.com: Replacement Upgrade Earpads Ear Pads Cushions Cover for Koss Porta Pro PP SP Sporta Pro Koss KSC35, KSC75, KSC55, KSC50 Headphones : Electronics