Well, I saw the MoM exhibit at the Smithsonian very shortly after it opened. That was back at the end of 1997, and I took a bunch of pics of the 5' Falcon.
The piece JPagaduan asked about looked the same in my pictures.
Actually it is. Im on the Falconbuilders group on yahoo and saw your site when you sent out the email. Awesome photos! I went to the exhibit when it was in LA. I took quite a bit of pics myself. Unfortunately, out of all of my sidwall shots I took, there was a glare from the flash on that 1 piece! UGH! I took alot of 90 degree shots(front, sides, and back). Lemme know if you need some specific shots.
I'd say its a replacement/repair part. Even the titan 90 railing is missing above the part in question. The 5' is missing quite a lot of parts. Every "black" area is generally a missing part.