I can tell you that it's definitely NOT a bent nail in the graflex clamp. It is in fact a lever. Not a graflex lever to be sure, but a lever. The tension on it seems loose and so it flops away from the clamp allowing the clamp to rotate around the saber's body. The pommel cubes, D ring and cone knob change position throughout the movie.
When you examine how the saber is constructed you realise that the whole end of the V2 from the in front of the Cone knob pointing backwards comes off to allow you to get inside at the motor that orginally spun the shaft.
Research makes me believe that the V2 which Mark wears (mostly) on his belt and which features in all of the studio shot footage, was infact the Obi-Wan stunt version that you see in one of the posts above. It is cast from the wooden master that was offered up on eBay a couple of years ago, and matches the Obi in all its dims, even down the heavy black paint that covered it.
I also believe that the Shared Stunt as it's known on the POSW site, never saw light of day in its current incarnation in either ANH or JEDI. It looks like it was cleaned up to look like the Luke "hero" saber after the fact. The copper paint on it's neck covers a much darker mix of black, and the slim emmiter face has been unevenly ground down to a flat surface but still has traces of lack paint embedded in surface pits and scratches. However the graflex band with the holes in, and the graflex lever ARE on the saber Mark wears whilst scrabbling up the side of Jabba's sail barge so it's probable the Shared Stunt, as its become known, was used as a stand it there.
What we've previously believed to be the "hero" version, was used extensively in ROTJ, but it was in fact the STUNT LIGHTSABER. When Mark catches the lightsaber on the skiff he catches the V2. When he fights with it, the bladed version he uses has the same body as the "Hero" version. Kind of makes sense since they weren't using a revolving blade this time, the ricketty old ANH stunts weren't used. At least NOT in Yuma. Instead a solid machined handle with no groove in the neck was used with a blade attached using a set screw in the nipple.
The V2 was an old Obi Wan stunt lightsaber that was pressed into use for live action filming. The "hero" that was used in the extreme close-up in Vader's hands, is I believe a stunt lightsaber without the blade attached.
I hope that clears everything up
Barry
