You have a K-22 Outdoorsman from the early to mid-1930s. They are often referred to as the K-22 First Model and did not have a barrel rib. The post-WWII K-22s were the first to have a barrel rib and had the letter K prefix on the serial numbers.

Excellent revolver and I would predict a very smooth action. Enjoy it as your Grandfather did.

Russ