Wheel-A-Matic caster/camber gauge opinions

I recently picked up a used Wheel-A-Matic WA601 caster/camber gauge. It seems to be in decent condition and I'm looking forward to learning how to use it. For those of you who've used one, what is your opinion on it and what was your experience?

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Gonna clean up the magnet, of course.q3FPKvTDSVmB6sAKWxkzBA.jpg