Watch out! As "disconnected" from the social inner circles as some of us are, we might accidentally adopt a hand sign which mimics a gang signal, and we might wind up with a tragedy someplace where an Aspie is mistaken for a Hoover 13 Krip, or something.
How about just announcing out loud "THERE ARE THREE BURNED OUT BULBS IN THE BUILDING!! !!" , OR "WHY IS THERE ONE MISMATCHED CEILING TILE" when you enter a restaurant... Anything that's clearly an out-of-context observation, voiced awkwardly.... That will let every other Aspie know you're one of us.
I wear a MedicAlert bracelet, which tells emergency personnel that I might freak out and hurt them/myself if restrained or wake up under bright examination lights, etc. As far as for social situations, I have tried to hone my "Aspie Radar". I have no problem openly discussing my Autism, but there are times I wouldn't announce it; such as at a motorcycle riders' club gathering, or when writing a politically-charged newspaper editorial. There are times it could be used against us, or other times it might help us. I have a marking on my driver's license, which says "High Functioning Autism may appear as nervous or guilty demeanor". This seems to help cut the number of times I get held and held by police, who spot my unusual behavior, and think I'm planning a bombing or a government take-over, or something, LOL.
As far as fellow Aspies and the HFA community identifying me as on the Spectrum, I have a puzzle piece bumper sticker, and wear a puzzle piece pendant, and I have a huge tattoo of an air raid siren made up of puzzle pieces with one missing, on my left shoulder. If that isn't plain enough, I'd have to wear a spelled-out T-shirt.
Charles