It’s not specified - he never has the Ring in the Hobbit - Bible finds it before we meet him.

In LotR it’s revealed that he rarely wore it anymore by that time.

Bilbo doesn't see him wear it, but he's described as having put it on to steal goblin children for food. So he does wear it in the books.

Its on such an expedition that the ring "slips" from him, further suggesting the ring is actually not only his size, but a little large.

> Its on such an expedition that the ring "slips" from him, further suggesting the ring is actually not only his size, but a little large.

It's heavily implied in LOTR that the ring is able to change it's size to cause itself to slip from a person's finger, though that's somewhat out of scope and the illustrator may not have read that.

It's unthinkable that a single, unchanging ring size would fit both Sauron and Gollum.

Sauron is known to shapeshift but maybe the dirty secret all along is that he’s hobbit-sized.