I've been searching for some vintage model kit parts that were used on some Star Wars blasters. During my search I noticed the similarity between the trigger housing detail on the ESB Rebel DH17 and the side greeblie on the Boba Fett ROTJ blaster.
Well, turns out they are one and the same. Flip the Fett greeblie 180°, cut it in half and you get the DH17 greeblie! The reason they don't look identical in the photos is because the model kit part comes in two halves and I couldn't find a good picture of one side, so you're seeing the R side on one blaster and the L side on the other.
From top to bottom. ESB DH17 blaster greeblie, Boba Fett ROTJ blaster greeblie.