American Herring Gull or Ring Billed Gull?

I saw a bird this morning on a field. It was with a flock of Black Headed Gulls and a few Herring Gulls. I see the same Black Headed Gulls and 1-2 Herring Gulls every morning, but there was an identical gull to a Herring Gull, except with a black beak tip. I assumed it to be a rare Ring Billed Gull, but checked and thought is was more likely an American Herring Gull (non-breeding). I didn't get a picture. Of course, every birder would hope it to be the Ring Billed, but I won't completely disappointed if it turns out to be a North American subspecies I've never seen before. 

However, I was going over some of my photos and found this which is fairly reminiscent of my sighting. My bird has a prominent structure, identical to the features of a Herring Gull in every way but the beak. 

Here is the old photo. There is a black ring on beak.