This lightsaber is somewhat unique among all the others. It and it's sibling the Luke Skywalker ROTJ II lightsaber were used to represent two different lightsabers on film. In Star Wars: A New Hope, they were Obi-Wan Kenobi's stunt lightsabers. They had "blades" covered in Scotchlite to reflect the set lights and simulate a glowing effect. Later, in Return of the Jedi, this one was used as a stunt version of Luke Skywalker's new lightsaber while the other had it's blade removed to become another Luke lightsaber stand-in. In fact, all of the rest of the Luke ROTJ sabers were modeled after these two.
There were no modifications made on this prop between the two films as far as we can tell. The stunt blade was probably removed after the filming of ROTJ and the prop was likely cleaned up a little. The copper paint and silver lines around the top grip were always there as seen in these still frames from ANH.
The copper is barely visible here, hidden by the shadows, as are the silver grip lines.
The prop was constructed by the floor effects team from A New Hope as a duplicate of the original "hero" version Obi-Wan Kenobi lightsaber. A master copy was made of wood and then cast in metal for conversion into stunt sabers. The conversion included a motor inside the handle to spin a dowel "blade" with flat sides, some covered with a highly reflective material. An electrical cord ran out the bottom of the saber hilt and up Alec Guinness' sleeve to run the motor. The glowing effect of the sabers blade was a combination of on set camera tricks and animated enhancement. A light was mounted on top of the camera and the scene was shot through a half-silvered mirror to capture the full intensity of light from the alternating reflective material of the blade. On set the lightsaber didn't look like much, but through the cameras lens it shone like a blade of energy. To give the blade color and a softer glow animated enhancements were made during post-production. At the time ILM was a small company just starting out so the lightsaber glows were assigned to Barry Nolan of VanDerVeer Photo Effects.
The replica sink handwheel on the bottom was a separate piece and cast (probably also in metal) from a wooden master. The shinier metallic sections (above and below the protrusions of the handwheel, the middle band, and the emitter head) are all chrome tape. It's possible this chrome tape was added after ANH to fix up the saber for use in ROTJ. At various points along the saber's shaft black set screws can be seen. There may be a screw under the chrome tape on the replica handwheel or it could have been the hole for the electrical cord. The face of the emitter is probably a steel fender washer.
A real Graflex flashgun middle band is on this lightsaber, though there are a couple holes drilled into it and it's been covered by chrome tape.
Graflex 3-cell Flashgun
On the replica handwheel, a D-ring was added through the rectangle lined up with the control box.
It is unknown what the gold and black striped piece in the Graflex clamp is. It may be just gold mylar tape on black plastic. If this piece was always on the prop, it may have inspired the change from calculator bubble to circuit board connector in Luke's ANH to ESB lightsabers.
In preparation for filming The Empire Strikes Back Mark Hamill and David Prowse (black and white photo) both practiced dueling with this lightsaber.
"The Making of The Empire Strikes Back"