Boba Fett has two versions of this rifle, one is a black variation seen with the Super Trooper and Preproduction 1 costume and a blue/grey variation seen with the Preproduction 2 costume.
(The term "Laser Rifle" is defined in Batha Tracks #5. It is sometimes referred to as either Laser Pistol or Sling Gun.)
The Laser Rifle is used with the Super trooper, Preproduction 1 and Preproduction 2 Boba Fett costumes.
The base of the Rifle is made from a Kaiser Camera Shoulder Stabilizer.
The barrel of the Rifle on the PP1 and Super trooper is a King 23-30 teliscope, on the PP2 the barrel is a Tasco 15x20-30 teliscope
This weapon is simply refered to as a "pistol" in Mark Harris' original paperwork.
Laser Rifle Version 1
Laser Rifle Version 2