I have an Apollo Mikron razor that I love. The calibration was off one-half digit, and I did not have the key that rotates the adjustment sleeve inside the handle. So I took a penny, placed it in a vice and cut off with a hacksaw a small portion of the penny on each side. It then fit the notches on the adjustment sleeve. I placed the razor on my makeshift key in the vice, turned it, and the calibration is now perfect: a setting of 1 with a loaded blade and the adjustment turned down to its mildest setting.
And the tool only cost me one cent!
And the tool only cost me one cent!