This is marked as a Norlab gas flow regulator that is preset to 0.3 LPM, with a max inlet pressure of 500 psi. Built in input pressure gauge reads to 700 psi. Quote from the Norlab site: "The 400 Series single-stage, piston-style regulators are designed to deliver a preset flow of non-corrosive gases in the 17 liter or 34 liter non-refillable cylinders with CGA 600 inlets. Each regulator comes with a cylinder pressure gauge." (HOWEVER  , The gauge is also marked with model PR150-03-500, which seems to be a Victor number. The Norlab number NLB414 is taped on) I am inclined to believe it is actually a Victor unit.  It looks new, but I don't know the history of it, so I will list as being used.