Holy conch fritters!

As I was poking amid the beachside ruins of an ancient civilization the other day, co-adventurer N walked up with this in his hand. I knew it was a conch of some tropical kind, and way out of range, but not more than that.
Bringing it home (it was 8”x7” and heavy; one of these days, the NYPD is going to ask me what's in my backpack and I'm going to get some weird looks when they start poking around in there), we get the low-down: Eustrombis gigas, the pink or queen conch, home of what the Wikiauthor calls the “very edible sea snail.” But what the hell was it doing in Brooklyn? Well, Dead Horse Bay’s crumbling shoreline, as a depository of decades of mid-century and earlier garbage, does offer up the most remarkable things now and then. Someone somewhen threw this away -- but had they or someone else carried it north, a souvenir of a holiday in the sun?
Or had they, dreaming of Brazil ("we stood beneath an amber moon..."), purchased it at the wholesale gastropod store? Or had some migrant from the Caribbean brought it along for homesickness's sake?

The Mysteries of Brooklyn are unending.