Unfortunately, it's not a spinner, it's a paddle. A spinner freely rotates 360 degrees, and is (almost) always an optical device. A paddle has a limited range-of-motion, and is (almost?) always a potentiometer device.
The NES version of Arkanoid is virtually un-playable past a certain level without that controller, though. I've never researched it, but I'll bet it's worth buck$ to serious NES collectors in working condition.
edit: According to Ebay completed auctions, it's not really that valuable after all. Bummer.