I like the Security series guns in general, but have found many with excessive play in the crane, what amounts to cylinder endshake, even on new ones. I note that when Manurhin in France made their version of the Security-Six, they incorporated a pin that seems to engage the crane when the cylinder is closed. I presume that they decided that the situation needed fixing. (Their gun is the MR-88, not their MR-73, which is more like an S&W with modern improvements.) I have seen the MR-88 only in photos.
When this situation is bad, the cylinder even touches the barrel as the gun is cocked. I think the front crane lock on the GP-100 was intended in part to cure this ailment, which (for some reason) no one has mentioned in print.
Lone Star