These blasters, from Return of the Jedi (as in the above picture), were actually based on the MGC (Model  Gun Corporation) Sterling replicas.

The overall design is based on the BSA Model 1949 prototype shown below as compared to the Sterling L2 as it was with the BlasTech DH-17's from ANH and ESB. In fact these were more replicas of those props than anything.

To the end of replicating the originals the modifications to the MGC replicas were rather extensive. The more major ones include the removal of the folding stock as well as the sawing off of a major portion of the barrel. An end was then fashioned for the prop to resemble the BlasTech DH-17's from ANH. A scope mount of sorts was attached to the top of the gun in the form of a rod detail that continues forward over the front of the gun. A casting of an old Single Point Red Dot Scope, similar to the model below, was added to the top of that (attached with unidentified scope mounting rings.)

To either side of the rod on the top of the gun were added small springs. Below the springs on the left side of the gun five small round detail pieces were added. It is unknown what these are at this time. Slightly behind these, two pieces very similar to the Revell piston halves, possibly custom made to resemble the piston halves, were screwed onto one side of the gun.

Another modification of note is the addition of rubber feet to either side of the original MGC rear sight. Like feet can be found on Han's ROTJ BlasTech DL-44.