These are very rare indeed! It's a wrench designed to hold the small collars on the base of the chrome tops of antique seltzer bottles. You then use the wooden block to turn the heads off the bottle while holding the collar with this special tool. The claws of the wrench are grooved perfectly to hold the collar without damaging them a bit. This one is embossed Starman Syphon Co. Brooklyn New York. Don't damage the tops with pliars or channel locks as the tops are made of lead. I'll do it for you
Wow! That's pretty cool. It's nice to have if you got stubborn tops that will not come off. I've often found that many seltzers can be opened by hand with the same principle. Hold that 2-part base in one hand and then turn the spout section counter-clockwise in the other. They sometimes pop right off. The tool is the perfect back-up. Plus, it is probably collectable in it's own right.