Im not so sure that is for grease, it looks way too ornate. Perhaps it injects oil into some piece of industrial machinery? I like the acme style adjustment screw. Hopefully someone can identify it, that is a really neat piece!
It is a grease gun. I wish I took a pic before I redid it. Well, I better rephrase that; there was grease in it when I disassembled it. The end of the nipple is internally threaded, if that means anything.
The research i done on those years back it was used to fill hydraulic knee action shocks on ol timey cars/trucks. I had a photo saved of a shop manual using 1 on a truck. But that puter fried couples years back and lost pic. It prolly had extensions/other fittings that threaded on it. That said i guess u could put anything in it and if it worked.... there u go.