I didn’t know that. I have seen several with broken swivel bases over the years. It seems to be the weakest point. There are a couple on eBay now with one of the mounting ears broken.Also, not all of the bullet vises had swivel bases. If you want swivel obviously keep an eye out for one but the one above may not be missing the swivel, it may not have come with it.
I think if it has a "N" on the end of the part number, it was a non swivel and if it has a "S" on the end of the part number it was a swivel.
350N = 3.5", stationary/non swivel
500S = 5" jaws, swivel
I do need it to swivel though. I’ll edit my original post.