Small Round Paint Sponge / Dauber
If you're an avid watcher of Debi's videos then you have probably seen the one where she puts paint in the freezer to thicken it up. She uses a number of tools in that video to create a funky layered paint effect, including some larger paint sponges, similar to this one. This is a smaller sponge with a plastic handle for working in more confined areas.
Measurements: 1 1/4 diameter x 1 1/2 long"
See second pic for size comparison to a quarter.
You can watch Debi's video here on YouTube