Help identifying shower handle (or what was the shower handle)

[Nick Smith]

I'm purchasing a property that requires a couple of minor diy fixes upon possession. In the shower, the handle is missing. The stem makes me think it was a Knob that went up and down for on and off. Then rotated (?) for cold or hot water. 

I've completely replaced two shower plumbing systems, but haven't seen a shower valve like this before. Does anyone know if there's a temporary fix; like a handle that can be attached to this stem? 

I'd prefer to not have to access and completely replace the shower valve system. I appreciate your thoughts.