Doubt about replacement

So, my brother's M17x R1 (refurbished) was replaced 6 months ago with a fully capped l521x (new). However, even after multiple calls, Dell has not picked up the M17x, so I was wondering if it would be OK if I sell it or something as it is collecting dust in the basement atm.

The laptop was bought is USA 1.5 years ago, but it was replaced in Peru with the International warranty. It has remained in Peru since them as my brothers now lives there.

Thank you.