Yeap, I have been doing it for a long time. When I get a bow, I use a lacquer pin and a thin steel pocket ruler. I lay the ruler on the surface of the limb and then mark the cam where the ruler touches the cam. I do this in a highly visible color. Usually, silver on a camo bow or black on a bright finished cam.
I also turn down the limb bolts and mark one side of the bolt, so I can count turns easier.
Later on, if I find I like the cam rotated differently than when it cam, I can remove the lacquer with lacquer thinner and redo the mark. Most manufacturer do actually have some reference for their cams. It may not be a mark. Center shot reference would probably be a good idea.
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