The story has it that a series of blasters were built for the Tatooine sand trooper scenes. The blasters have the letters “ILM” engraved in them.
I have not validated this story, or the claims of the origins of this prop.
This purchase was actually quite a bit of a disappointment. I purchased this prop along with a Return of The Jedi Leia blaster from the same maker. The castings were quite poor, with low grade clean up performed. It looks as if a very low grit sand paper was used to clean up the seams. The paint job is not to spiffy. Even worse, when the blaster arrived, the scope was broken off it. The seller did not offer me a replacement or a refund.
Due to the poor customer service and sub par quality of the piece, I refrained from purchasing from this dealer again. As it turns out, the guy is a super nice guy who is very knowledgeable.