Help with tub/shower stem?

Sorry I have no idea what I’m doing, and can’t find anything similar to this online. My grandma’s tub/shower has two knobs, the left (hot) broke the last time she used it, causing the knob to spin without being able to turn the water off. I came over and shut the water off, and took some pictures and I’m hoping someone can give me some advice. The stem seems pretty different to anything I can find online.

Intact stem on the top, removed from the working side to see what it looked like. Bottom is the piece from the other stem, the threads part broke off in the pipe.