I believe Catbus has created an exact match from screen captures for both the ANH and ROTJ. They are virtually identical. From what he found, it is not surprising to hear that the OT were custom made. From his observations, the original is Franklin Gothic slightly rounded.

And with fonts, what is in a name is the general shape and characteristics of the letters. There can be slight variations from vendor to vendor on how the font is rendered that can change things slightly. With the fonts on my computer, the fonts that Catbus created seem over bold. Almost as if it were Frankling Gothic Demi Condensed but over exposed, giving it an extra bold and rounded look. And from my attempts to recreate pre-computer age typefaces, a great many were modified during the transition. I have one where the lower case y was changed, but every other letter is identical. They probably used a standard typeface that has been altered when they created the font.

(Note: From a technical aspect, the typeface is the design of the letters - it can be patented, but not copyrighted. A font is a vector graphic representation of a typeface that can be scaled, compressed, expanded, warped, etc. and is copyrighted… until you render it as a bitmap and lose the unique vector points.)

Also, I just checked the TPM alien subtitles and they are nearly identical to the ROTJ one. They are slightly narrower, but the same typeface. The lower case g is slightly different, so it isn’t an exact match, but very close.