A pencil line on the cam. I've never marked it, just loosen the Allen head screw and move the cam a slight bit and retighten the screw. What I just posted came from a different web site. There were two different replies of someone having the same problem. Some of those guys have been reloading with Mec's for many years and seem quite knowledgeable. I've learned a lot over there [
www.shotgunworld.com ] in the reloading forum.