There have been pitch gauges for sale since the 60s. I've had two different ones since then. They both were capable of very good accuracy for measuring the angle of the back of the prop. No gauges that I've seen made any attempt to measure anything other than that. It was up to the user to match the tool to the profile he hoped to measure. Luckily most props are relatively flat bottom airfoils. Unfortunately, very few flat bottom airfoils AOA match the angle of the bottom. And of course, to expect a prop-profile's AOA to advance at the "pitch rate" fails to understand what's actually going on with that means of propulsion.
But it's about all we got to work with. So measuring the pitch however you do it at least gives you some means of describing something about your different props.
One thing you discover with a pitch gauge is just how far from perfect our model props are. And about the time you recognize that, you discover how little that matters with our models.
Back in the past, the C/L speed guys and FF guys were carving their own props and had an excellent situation for judging their handiwork. They were some of the first to produce prop gauges. The C/L aerobatics guys also had a few who were that serious and some Rat Race boys. If you know any of them, they'd be worth talking to in order to dig one up. I don't think I've ever seen one advertised by a model retailer. I think one of mine from the old days was made recently by Edmunds Engineering. Yup... found a pix... Can't find them however.
You should notice how limited the prop size is...