One observation to note that I don't think I've made public as of yet, the Merr Sonns were cast from the original Mauser before the lower frame was changed of course (as we've all already know, thanks to lonepigeon many years ago)...but there have been theories over the years circulating that there was a casting made from the actual Hero, complete with the correct, replaced lower and original flash hider (which is was), but the theory suggests that it was cast for ANH and 'Before' ESB started filming, then later used as the ESB and ROTJ stunt blasters..
However, although the ESB stunts are indeed cast from the exact Hero ANH blaster, they also have greeblies (clearly present before molding) cast from that mold 'into' the left side, from the Revell Visible V-8 model engine. Right over the area where the Mystery Disk should be..(also, on top of the mystery of the disk's incorporation, aside from this particular discussion, if the disk was permanently present to begin with..it doesn't show in the stunts). These are greeblies that were primarily seen on ESB props, never on an ANH Mauser whatsoever.
Thus suggesting that the ESB/ROTJ stunt blasters were very likely molded and cast sometime after ANH, as Pat (kpax) also noted a few posts back.
The pre-existing, molded-in ESB greeblie evidence to me seems fairly solid considering that there are no Revell V-8 engine parts ever seen present on an ANH Mauser-based blaster thus far, even the Merr Sonns.
P.S...probably should have posted this in the ANH Hero thread instead, for continuity..and somewhat irrelevant reasons..haha =b
-Carson