【Operation Unknown】 Wonderswan Headphone Adapter Sammy wonderswan

This is a used headphone adapter for the Wonderswan made by Sammy.
This is the adapter only, and no other accessories are included.

I found it while doing a major cleaning, but I don't have the actual device, so I haven't been able to test its operation.

There are no noticeable scratches or dirt, but there are scuffs from use, so please refer to the photos for details.

Please be careful about the shape of the compatible 3.5mm stereo mini plug.
Plugs with a microphone function, which are common these days, cannot be used.

Please refrain from price negotiations.