There does, in fact, appear to be extra holes. Surprised I didn't notice it, or anyone else for that matter! Why is there a hole in the middle of where the Knobby is located? Did someone attempt to use a Swivo holder at this location? That hole doesn't look factory to me. Based on that, it's possible the Knobby was also installed at a later date.
Good point. I thought what happened here is that they drilled for a cymbal mount that's telescoping and instead put one on for an L-arm.
Also wondered why they'd maul the tag; or place one there knowing that if a mount was added it'd be skewered. Guess: they made the shells 1st and then filled the order when it came in. Sloppy tag placement nevertheless.