Well, Jimmy from Brooklyn informs me that the signage I saw was in fact incomplete, and that he managed to snap a shot of the finished sign this past weekend:
I'm not sure this is elucidating or obfuscating. (Though it's definitely interesting, and potentially delicious.) Certainly the sign makes sense now, but not in the context of a bike shop. Is it possible that Dah Shop's management, fearing the imminent Apocalypse, has abruptly changed direction and is now focussing on soup instead of bicycles? If so, will they offer a variety of soups or just chowder? And if it's just chowder, will they focus on clam, or will they also offer less popular but equally savory varieties such as fish, corn, and seafood? Or maybe they'll sell bikes and chowder side-by-side. While that would be an unusual combination, there's probably room in New York City for a bicycle-and-chowder boutique. Actually, now that I think of it I'm kind of surprised it hasn't happened sooner. I'd hate to get ahead of myself, but if this formula proves successful they could even branch out into cheese.
Of course, I'm not dismissing the possibility that this photo is a hoax. I find it strange that the exact same cars are parked in front of the shop in both photos. Also, the shadows in the second photo are in the exact same positions as those in the first, which indicates either that I'm being had or that Jimmy happened to show up at Dah Shop when the sun was in precisely the same position in the sky as it was when I visited. Jimmy's spy shots of the new Dura Ace also proved to be wildly inaccurate (though oddly compelling), so I'd be wise to take this with the proverbial grain of salt.
Hopefully further evidence will come to light in the near future. When it does, I'll advise you as to whether you should show up at Dah Shop with your bicycle or your appetite. (Or both.)