It’s a skeleton hand placed on a 2x2 Gridfinity base. It’sBodyParts3D Hand Skeleton created by Lambchops - Thingiverseadaptation

This model is part of the continuously expanding “Gridfinity Anatomy” collection. You can view the full collection here:https://makerworld.com/de/collections/10042958-gridfinity-anatomy 

Important note:To view all the models in this series, you must enable “Show NSFW content” in your account settings. This is necessary because some anatomically accurate models are marked as sensitive content by the platform.

How to enable:Account Settings > Settings > Show NSFW (bottom)