The marking device for pottery was also used as a cutting tool to ensure the pot was the same size as the last one…with the same shape at the cut too. That’s how I saw it being used at a College demonstration once.
I’n not convinced about the others being a valve grinder, the valve needs holding by the valve end, and pressure applied to it so the mating face beds with the female part in the Cylinder Head. That’s why today’s tools is just a wooden stick with a sucker on the end.
This pictured tool would not give a smooth enough movement, nor can it apply pressure from the correct direction.Could be wrong, but I’ve ground a few valves in my time.