I was not sure what a compression tester actually did, so I checked the online definition (hooray for Google) and got this: Compression testing is a very common testing method that is used to establish the compressive force or crush resistance of a material and the ability of the material to recover after a specified compressive force is applied and even held over a defined period of time. (I didn't say I would understand it though.)
Great piece of automobilia, made by the Peerless Company, I believe. The handle opens up to store an extra tip and a longer attachment to reach where fingers can't. The extra pieces are not included however!