This is the SONY Walkman WM-2 dynamic headphones, model MDR-4L1S. Sound from both left and right sides has been confirmed. The mute function, activated by pressing the WALKMAN button, has also been confirmed to work. - Model Name: MDR-4LIS - Brand: SONY Walkman - Type: Dynamic Stereo Headphones - Cable Length: Standard length - Design: Open-air type Released in 1981 SONY DYNAMIC STEREO HEADPHONES MDR-4(L1S) These headphones were developed for the second-generation cassette Walkman WM-2. They are lightweight and open-type, making you almost forget you're wearing them, and they offer excellent sound quality. They can be used with devices equipped with a standard 3.5mm mini-jack, such as players and smartphones. Pressing the orange "WALKMAN" button on the splitter activates the mute function, allowing you to hear external sounds.