Jim, the Unclenick protractor thing is already at hand. Read post 29 in this thread regarding his lables to put on dies. I supplied a picture showing how they look. The instructions in Unclenick's link explain how to use them.
They are not sloppy at all when correctly used. I've been doing the equivalent for decades and sized case headspace tolerances are typically less than .002". Good enough to shoot bullets as accurate as anyone else can. That dimension's spread is the least important to make very tiny.
I brought the idea of marking die lock rings to RCBS decades ago. Their rep thought it was a good idea to go along with their micrometer type competition bullet seater and Precision Mic case gauge. My idea was to stamp one side if the lock rings with 72 radial lines spaced to represent a .002" change of die height. RCBS never did it.
Here's a link to related information:
http://www.beartoothbullets.com/tech...h_notes.htm/74