I knew you were goin to have a field day with that one. Bob Munden used to fix the timing so that it didn't make a mark.Colt cylinder only gets marked 2 ways,.
Least common is a mark just outside the lead because cylinder bolt timing is several miles off, not likely on a factory gun.
Most common is the drag line which comes from incorrect operation... specifically lowering the hammer from less than full cock.
Grips and spring prolly.

