Quoted from gutz:The two horizontal pieces near the bottom middle have 'flipper' written below them, but they don't look like normal flippers
That type of flippers were standard United fare in the late 40s. There's a small metal bar that connects the two posts at the bottom. They have a very different feel to them, since they're "hollow." They sling and bounce the ball when used, and they have a surprising amount of snap to them.
I seem to remember that this style of United flippers operated like the William's impulse flippers though, where one button would operate both, but I don't remember if that was the exception, or it was used in all their games.