Case and point, meet Jim R., a Hollywood cinematographer who I spotted from at least 1/4 of a mile away arriving to SSC on his sport bike (Yamaha R1 I think, but they all look the damn same these days). His helmet is one of two original helmets made for the 1991 film
The Rocketeer. In the film, Cliff Seacourt, a stunt pilot during World War II, finds a Nazi jetpack in a hangar. His mechanic/best friend Peevy, played by Alan Arkin, builds the helmet for Cliff with an integrated rudder, which helps Cliff steer while flying around the Los Angeles area using the jetpack. This particular helmet was the backup in case the primary was damaged during filming, and Jim scored this amazing souvenir after the movie wrapped.
The helmet itself is made of brass, and it’s surprisingly comfortable. I tried it on, and could see very clearly out of it, as well as breathe easily. The top 3/4 air vents are functional, and keep the scalp cool while riding/flying. The inner padding is lacking by 2010 standards (it was a WWII movie, after all), and it takes a brave man to actually wear this thing while riding a motorcycle.