Need help identifying part

[MAC702]

One of my range pals brings his out to the monthly subgun matches every once in a while. He really likes to bring it out in February, because that's our Valentine's Day match, when all of us with Tommy Guns have our own division. And the cheap-*** Grease Gun will kick a Tommy's *** in a match that depends on hits plus conservation of ammo. I keep looking at the ones that pop up on auctions, but just haven't been convinced enough to do it. Other guns are much higher on the collection list.