Testing your razor if it has negative or positive blade exposure can be hard to do from my experience and how close to negative or positive blade exposure, manufactures will determine that for different reason and either type of blade exposure seems to work from using my different razors. The way I do my blade exposure test is using some spent blades and making two shims and a modified blade trimmed only half way on the blade edge and as flat as possible. Razor Blade Shims are .004 of a inch in thickness(see reference #33 on how my shim looks for good results) so that becomes our measuring device to see how many are needed, most of my mild razors I found were negative to neutral and some of the more aggressive razors are positive and not to far from the neutral exposure area. The tools needed safety glasses, tin snips preferred or scissors, a hard piece of plastic(plastic hotel key) & honing stone to knock any high spots on the modified blade after cutting and I made it more of curious fun project and for the keeners who are like to know more about their razor. The pictures are better at explaining than I am so take a look. I used a adjustable razor so it can be shown better and illustrations more pronounced, the modified blade becomes the testing piece(standard). Modified trimmed blade, stone hone any high protrusions created from tin snips and keep blade as flat as possible. When you feel the bump of the plastic on the razor blade corner edge the razor now has positive blade exposure.(you have entered a aggressiveness area of this adjustable-take a note for future reference when setting this razor if memory fades a little.) Some times you can see the blade exposure against the plastic backdrop with your eyes or better yet a Jewels loupe magnifier but bump feel is just as good or better. For 3 or 2 pc razors the .004 thou shim is added to bottom for testing negative blade exposure which is usually 1 or 2 shims at most until you feel the plastic touching the blade edge corner. For positive blade exposure known razor(r41) I would add the .004 shim to the top of blade and tighten cap to increase razor plane until the blade and plastic does not touch. This determines approx how many thousands of a inch the blade is positive. This modified blade can also test how accurate the blade sits in the razor on both sides when clamped.(amazing how inaccurate a sloppy blade seat or posts are when machined with a lot of tolerances by checking both sides of razor with the modified blade test pc.) Hope this is not to confusing and to most they might not have interest because they want just to shave! Update: bought one of these USB microscopes for my hobbies a few years ago and share a few captions.