The keys have "Concentric Tube Lock" one one side.
It works similar to an Ace 7 pin lock (or similar) in such that you insert the key, pushing it all the way straight in and this moves the spring loaded tumblers to the shear line. There are only 3 tumblers, one inside the other. Once the tumblers are pushed to the shear line, you can turn the key clockwise, rotating half the lower body and opening the lock.
The first pic shows the closed lock, the keyway and the tumblers not at shear line:
The second picture shows the pins at the shear line and 6 different Wise-Lock keys.
