Dwell readings changing?

He has points and the dwell is jumping around but the timing is steady. He is getting bad dwell readings and very likely does not have an issue with his distributor.

BTW, mopar solved the too much dwell at low rpms by using a ballast resistor. By definition a ballast resistor varies it's resistance with temperature. At low rpms the current flows for enough time for the ballast to get hot increasing it's resistance and reducing current flow through the coil and keeping it from over heating. At higher rpms the current flows for less time so there is not as much heat build up in the ballast so the resistance is lower and more current flows resulting more coil output.