I'll take a stab at it. I don't know which game that is, but I'm going to assume it's a Bally since it looks different than the (one) Williams zipper flipper assembly I've seen. So here are a couple snippets from the "Nip It" schematic. You can see there are 3 EOS switches that I assume are the 3 that you're looking at - 2 NC and 1 NO which is what your picture shows. I'd guess that your machine is similar.

zipper flipper 1 (resized).JPGzipper flipper 2 (resized).JPG

So it looks like in the top snippet, the NC EOS switch allows the "Close Flipper Sol" to be energized when a switch on the "Mushroom Bumper Relay" (M-B RE.) is closed, closing the flippers, which then opens that NC switch and cuts power to the M-B solenoid. The flipper must mechanically latch in the closed position.

In the bottom snippet, the other NC EOS switch on the right is part of the lock-in circuit for the "Mushroom Bumper Relay". That NC EOS switch keeps the "M-B Re." energized until the flippers are completely closed, at which point it opens and cuts power to the mushroom bumper relay.

In the bottom snippet, the NO EOS switch on the left side closes when the flippers are closed, and allows the "Open Flipper Relay" to be powered when any of the switches above it close.