Sony WM-F107 user manual and question

I've tried to locate a user manual for this, anyone have it?

Also, anyone knows what this detail is? See picture.

 

I have a boxed one with the user manual
it's a more or less typical manual , here are some sample pages no mention about the detail you ask though . My thought is that it's used as battery cable attachment for storage.















Either way but maybe I'm wrong :

 

Thanks! Yes it could simply be for the cable but its not a good fit.