From the look of it has had some use but not a huge amount as no major play in the derailleur. With some dirt on it alongside some scratches showing obvious use.
Great functional condition with plenty of life left in it!

A.I:

The Shimano CUES RD-U4000-GS Rear Derailleur is a high-quality bike component designed for cycling enthusiasts. With a sleek 9-speed shadow design and direct attach feature, this rear derailleur offers smooth and precise gear changes for an enhanced riding experience. As a product from the reputable brand Shimano, you can trust in its durability and performance, making it a great choice for serious cyclists looking to upgrade their bike components.