Plastic snapper novelty
The snapper has rightly been a popular novelty for decades. You demonstrate that, when you pull the plunger out of the tube, it snaps back as though attached to a rubber band. Hand it to somebody else and they will fail to get the plunger to snap back. However, as soon as you take it back you can repeat the effect. This snapper is particularly smart and is probably one of the type supplied by Davenports.