I have owned several 1911s. Have always carefully avoided, and succeeded in avoiding, the dreaded "idiot mark". I recently. acquired my nicest one yet,aSig target stainless. Took it apart, cleaned and oiled it no problems. Went and shot, came inside and cleaned it. Put it back together and slipped the pin right past "home" and up onto the slide. Owned the gun two hours and have a nice little half moon right on the slide. Arrrgh.