Beautiful Brown McCoy "Onyx" Vase / Yellow ware / Circa 1920's ?

This was on a sidewalk sale table outside the same GW where I found the Qianlong Punch Bowl . It's 6 1/2" tall with beautiful brown,tan and touches of blue grey colors. There is an unusual bump around the body which appears as a line inside the vase. It looks like it has a chip out of the base but it's a glaze miss were it didn't flow all the way to the bottom. The clay is a heavy yellowish buff color. There are no marks or labels. I've seen a green one on Ebay shaped exactly like this but they are simply calling it vintage American art pottery. Maybe McCoy Onyx yellow ware. -Mike-