Help. Weird plastik ring from walkman

Hi. I am a new owner of a tps-l2 sony walkman and are currently seeking help, with one possibly big question

Does anyone know where this has to go. It fell out of the walkman when I tried to change the belts.

Thank you.

 

Around the power plug?

 

Maybe yes, but I seems too small. Do you know if there is supposed to be a plastic washer around the power plug area?

 

I have no idea (on this WM).
But there was a very similar ring on my AIWAs ...

 

As long as it isn't something crucial for the functionality it probably isn't that important Maybe.
I suspect it might not even be from the walkman because no one seem to know what it is.
Thank you for commenting tho