I got that pic here on the RPF.
That's David Prowse from a British tv show made during/after ESB holding a weird Vader saber. I believe they were in Elstree on a SW set for the tv show, with some of the props and costumes on display. I guess is was '78-'80.
That should be one of, or made up from, screen used ESB Vader costume pieces.
Is that TV show the one where only one taped copy is known to exist and that was never shown again ?
And yes, that lightsaber looks really weird, definitely nothing screen used. Maybe this was promotional too ?
Michael