Koss K/135 (Mid 1970s)
A rare set of vintage over-ear stereo headphones from Koss. They have rectangular ear-pads with circular openings and a coiled cable.
Overview
The Koss K/135 is a set of wired stereo over-ear headphones made in the mid-1970s. Koss sold them under its "Stereophones" line with this slogan: "Slipping into the beautiful Sound of Koss has always been an exciting experience for those who love music. And with the all…" The slogan points to an emphasis on immersive audio for music lovers. Today the K/135 is known mostly through collector listings, and there is little technical documentation on it.
Design
The K/135 has odd rectangular ear-pads with a circular hole, a coiled cable, and a 1/4" jack plug. The original cord is still attached on surviving units. Models have been documented in brown and beige. They were sold with hangtags, which points to the usual retail packaging of the era.
Collectibility
Listings describe the Koss K/135 as rare. Surviving units are noted in very good condition, and some were tested as working with sound through both sides. Some units show cosmetic wear, but where tested, they work.
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