KE? ..... the OP wasn't sure if it was telescopic thinking there was possibly only one way to find out. to many that would not be the case! i proposed a simple way to discover if it was so, you would not be connecting inlet and outlet you merely want to push some air into the inlet port to push out the piston you might even be able to do it with a bicycle pump(if you are lucky)
Ross you'll need a short piece of rubber hose that fits over the thread that has the yellow cap and a hose clamp in the other end you 'll need a reducer , the cheapest will be a plastic(ldpe/hdpe) irrigation one from the local co-op , Build-it ,Mica. (those are in order of cost) probably R7 to R11. the other side to fit your compressor hose probably 6 or 8 mm.
if you don't have easy access to a compressor then go to your local tyre fitment shop and ask for an old tyre valve, cut off the bulbous bit and that will give you a 10mm rubber stem to stick into the tube . so all you need is two bits of hose , 3 hose clamps and a reducer if you have the tyre valve you can "test" at your local petrol (gas to our American friends)station. all for less than 1us$ that's R15 for us Ross. if that piston is in good shape it should require less than 1 bar or so to extend it, you are merely testing to see if it is telescopic or not.
Good luck Ian