So I wound up reading the "List of RotJ Luke Sabers" thread and this Sail Barge "mystery" saber is bugging the hell out of me. My initial feeling was that this is one of the cast RotJ stunt copies but the bug bit me, and after some researching, a really big part of me thinks this is the "Shared Stunt" before it was tinkered with to look like the thing we know today.
Blowing the image up, I don't think it can be the V2 because at this point, not only was the V2 all black, but the V2 had the mystery chunk and the transcriptor knob added, as well as maintaining the long lever, and in this photo, near the third pommel cube from the d-ring, we would've seen not just the mystery chunk, but the transcriptor knob as well. "They could've been removed", one might say but even if that were so, there'd still be a discernible hole where the chunk would've gone into, right above the pommel cube. This doesn't have that. However, if this
were the Shared Stunt, the hole would be on the first pommel cube to the left of the d-ring, just out of sight from us.
One thing that really bugs me in this image is that the upper neck looks too long to be any of the ANH stunt sabers. The Yuma stunt had a long neck and paint chipping on it too but keeping me from fully believing that it's one of the Yuma stunts is considering this next photo of the saber from another angle. Considering what we know of the Shared and V2's history together, the color scheme and the overall wear to the paint, coupled with the extent of how far the clamp lever sticks out, makes me really lean towards that this is the Shared Stunt, pre-Death Star 2 modification.
However, I still maintain one huge discrepancy about my own theory as to what this is and it lies in the uniformity of the metal's color and sheen. Not just on the saber body but extending to the clamp and lever. It may very well be the lighting, resolution, and whatever else affecting it, but the saber's color looks too uniform to me; very similar to the metal/resin cast stunts of the sabers glimpsed in the "Discoveries from the Inside" clip.
But again, it all could just be lighting, the angle of the hilt, and the quality of the image affecting all of this.