grease fitting unplugging tool

I actually bought this to unplug the oiling fittings on a used mill I'm trying to repair. I saw it advertised online, it's an IPA #7862. it says it's made in USA, and I tend to believe it because it's machined out of solid steel, with really nice, clean-cut knurling on the body. You pull out the piston, fill the internal reservoir with a light penetrating oil, replace the piston, turn it face up and lightly tap on the striking end of the piston to bleed off trapped air, then stick it on the fitting and tap with a hammer on the striking end of the piston and it's supposed to unplug the hardened grease in a Zerk. It comes in a case with another Zerk adapter and a short flex line adapter. I think it was around $30 w/shipping.