This was inspired by a project from Arthur Whitehead. I thought what he made was awesome! He used Cinema 4D and Octane. I wanted to see what I could do in 100% Blender, with no add-ons. The grunge textures were from #Poliigon, the rest is the principle shader.
I hope you like it, it took about 9hrs from start to finish, rendered at 5k samples.
The gears are mostly to scale, I modeled the watch based off a 45mm case diameter. The entire model is pictured below in a screen capture. Functioning wise, a few of the gears work correctly. The rest are just moved into place and animated for visual interest. I actually only have 3 gears in the whole watch, I just modified scale and thickness