My house is about 15 miles from the Fort Lauderdale Beach and I've never seen anything like what you describe with that watch. Like Doc said, if you stored your horn outside it might be a different story but I certainly hope you're no proposing that. I would think that buying a horn from an area close to the sea should be very safe as long as you know that the horn wasn't stored outside or used as a lawn ornament.
My opinion for what it's worth...