I agree. The ESB scope appears to be a type 2. I can also confirm that the ROTJ Hero blaster has a type 2 scope as well. The thickness of the eyepiece confirms it.
Can you confirm that the type 2 ASI text reads "A.S.I." while the type 1 reads just "A.S.I" (no period after the I)?
This seems to hold true from the scopes I've seen.
If so, I think I can safely say the the ASI scope used on the Rexim-Favor blasters in Alien were also type 2's. This is significant because those props were also made by Bapty.
Chris, I was always unsure about the ROTJ hero but I think you are right and I am in agreement, that is also a type 2 scope. I have observed that these type 2 scopes are significantly rarer than the type 1 scopes. This now also makes type 3 scopes more desirable than before due to the plastic eyepiece. The locking ring is easily swapped out and the objective bell is negligible.
As for the ASI brand marking, there are no differences that I can see: both are labelled "A.S.I.", I believe this has been the case on all ASI that I have identified or owned. The only brand for which I have seen variations in brand marking is the Sussex Armoury 4x20. I have seen three different types of brand marking on these. If you have detailed pictures of the Alien prop I would love to take a look. I have seen some pictures and as mentioned in the OP the scope has a type D mount. I have only ever found original ASI with type D mounts. I didn't include my opinion on this in the OP due to it's subjectivity but...............
My (purely, absolutely subjective) opinion is that it is unlikely that the scope used is the ASI as I find it unlikely the prop maker would have bothered to faff about changing the mounts. Ditto for the Sussex, only ever seen those with type C mounts in original condition (although this might make it a likely candidate for the basis of the ROTJ stunt). Difficult to speculate on the Jason due to the lack of information but if it is the brand of a US firm it makes it even less likely. The one pictured in the gallery appears to have either type A or B rings but whether they were original is unknown to me. My money is on the Milbro or Hunter due to the fact that they show up with original type A rings and as the Milbro is more common I'd say the chances are that it is one of those, that's for the ESB at least. Not sure with the ROTJ as I am unsure where it was made and who by. Was that Bapty too?
I had deliberately not displayed brand marking before because people are (needlessly in my opinion) obsessed with the ASI but in light of your post I have updated the OP with pictures of the different eyepiece and brand marking types. I have also posted pictures of original boxes too. I have used the best quality images I have available but as you will see some are not great. If anyone has a better quality picture where I have used a poor one then I'd be grateful if you could supply one and I will update accordingly.
Regardless of all this People should be aware that Chris and I are talking about fractions of degrees, mere millimetres (if that) and that I stand by my original comment in the OP that it would be unwise to pass up any given scope type at a reasonable price for a different scope type at an unreasonable price i.e. don't pay £100 for a type 2 if you can get a type 1 or 3 for £30 (or pay more for an ASI than any other brand). They are so similar that it is barely noticable, It still takes me some time to tell them apart when handling them and when I posted my updates and edits of brand marking above I had to re-edit the post because I had labelled the types incorrectly!
Of course this now means that my Type 2 Hunter is top pf my list: A hunter for a hunter
Original post edited and updated with new pictures and information regarding scope types (particularly the type 2) has been clarified. I habe not included my opinion on brand used in OP due to subjectivity.
Keep living the dream.
Andy