A simple squirt of brake clean on the shaft. If it then moves more easily, it indicates that it is a mechanical device and not hydraulic. Usually, friction dampers of this type are actually packed with rubber rings around the shaft and then compressed into the tube for resistance. A drop of fluid will make the rubber slide along the shaft easier. I suggest brake clean because it evaporates quickly and leaves no lubricant behind, unlike WD40 or carb cleaner. I believe Crusty's description is mistaken, just my opinion, and I am willing to be proven wrong. In fact, I would welcome it as I would like to have one if it really is hydraulic!!
Brian