Most manufactures have their own marking system for identifying heat ranges of their plugs, but I have some here that I have no idea where they fall, even from looking at the coil.

Is there a way a glow plug could be electronically measured to find its heat range compared to others? I've noticed with colder plugs they use up more amperage to reach the same visual brightness as a hotter plug.

How about using a set amperage and a heat temp gun?

Just putting a plug in and guessing how the motor is working to determine the heat range sometimes isn't the right first step.