http://www.adventure-supply.com/propresearch.htm


He also gave me some details (some of which I already knew, and some of which I didn’t). Lee’s jacket was partially derived from measurements of a jacket in the Lucasfilm archives. Lee had a contact there in 85’ that gave him jacket measurements of one of the jackets. What Lee didn’t know at the time was that the measurements came from a TOD jacket. At the time Lee didn’t make the distinction between a Raiders and a TOD jacket. He thought they were one in the same. There are obvious discrepancies between the two jackets, a few of which Lee addressed, since he was really going for a Raiders jacket.
The first was the pockets. Lee was told (By his collaborators at Flightsuits) that the pocket dimensions that he had were not what was in the Raiders pictures being used for reference (and it was obvious, especially with the TOD “midget pockets”). Lee had them make the pockets bigger to more closely resemble the Raiders pockets. Lee’s jacket also had one piece gussets, since this is all you could make out from the “stars” photo.
If you look closely at this jacket (it was the last one that Lee had made before his relationship with the old “new” Flightsuits dissolved), there are other differences between it and what was sold to the public (it’s too bad we don’t have access to one). As Lee learned more, he changed the details, at least on his personal jacket. The first is that this jacket is made of horsehide and not goatskin (this had nothing to do with anything other than a personal preference). Lee’s personal jacket also has rectangular sliders instead of pronged buckles. The production jacket that sold had single pronged buckles. Although Lee had contracted for double-pronged buckles with his vendor (and that’s what they sent him as examples), they delivered single-pronged buckles. Their story was that they no longer made the double-pronged buckles. Lee went with what they sent him. Another variance is that Lee had this jacket modified later (after it was originally made) to have 5-inch slit-openings in the back instead of two-inch slit-openings (which is how FS produced them per TOD spec).
One of these jackets was also sent to Peter. You can see some details that were incorporated into the LC jacket like the inside pocket leather facing. Cheers
PS- The site calls the jacket the “Keppler” prototype and this is how the jacket has been referred to in the past. However, the jacket is actually one of the last ones that Flightsuits made before they parted ways with Lee.
PPS- Here's a pic from the main Indygear site of Lee when the jacket was new.

Edit - Lee wanted me to make it clear about what the “New Old Flightsuits” was. Basically Flightsuits was being sold to new owners in 86'. The new owners weren’t cooperative with regards to the manufacture of Lee’s Indy jacket. What ended up happening though was that Flightsuits was never sold. The same owners today own the company. Lee didn’t find this out until years later.