Until recently we all though Vader's Lightsaber was based on a Heiland flash.  Thanks to The Parts of Star Wars we now know different.

Here are pictures of the illusive 3-cell unit was an MPP Microflash manufactured by Micro Precision Products.

Vader's ANH Lightsaber.

Vader's ROTJ Lightsaber (based on a Graflex rather than a Heiland or MPP)

Large image of Vader's ANH Lightsaber.

Vader's ROTJ Lightsaber.

A raw Heiland upon which we used to think that Vader's ANH Lightsaber was based.

Blueprints of the ROTJ Lightsaber.

An Icon's replica.

Vader's ROTJ Lightsaber from the Magic of the Myth expo.