Koss K/135 (Mid 1970s)
A rare set of vintage over-ear stereo headphones from Koss, notable for their unique rectangular ear-pads with circular openings and coiled cable.
Overview
The Koss K/135 is a set of wired stereo over-ear headphones produced in the mid-1970s. Marketed under Koss’s “Stereophones” line, they were promoted with the slogan: "Slipping into the beautiful Sound of Koss has always been an exciting experience for those who love music. And with the all…" — suggesting an emphasis on immersive audio for music lovers. Known today primarily through collector listings, the K/135 stands out for its distinctive design details despite a lack of technical documentation.
Design
The K/135 features very weird rectangular ear-pads with a circular hole, a coiled cable, and a 1/4" jack plug. The original cord remains attached in surviving units, and models have been documented in brown and beige color options. These headphones were sold with hangtags, indicating retail packaging typical of the era.
Collectibility
Listings describe the Koss K/135 as rare, with surviving units noted in very good condition, some tested as working with sound through both sides. Cosmetic wear is present on some units, but functionality appears intact where tested.
eBay Listings
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