Another one of my favorite lines when approaching strangers is, "I bought this thing on eBay. I just got it yesterday. This is the first time I've actually tried it out. Whaddya' think?" Then hold up your novelty camera for them to size up while giving them some background info about it. Or even just hand it to them.
With the Crown I will sometimes open the lens, pop the viewing shade (an impressive audio/visual in itself), then just hand them the camera and tell them to point it back at me while looking through the open shade. By the time I've finished explaining that pesky upside down thing, we're darned close to being old friends. And by that point they're usually thrilled to have their photo made with it.
It's a fact that terrorists and pedophiles DO NOT use antique cameras purchased on eBay. Or hand them over to their intended victims first.