This is a simple little tool used to open a codd bottle.
The marbles at the top of codd bottles were quite well lodged and difficult to open as the bubbles in the carbonated drink would keep the pressure on the marble to stay lodged in the top of the bottle. This tool was placed on the top of the codd bottle and given a little tap (a wallop) sending the marble to the recess at the side of the bottle. The drink could then be enjoyed without any problem of the marble getting in the way.
This vintage opener measures approx. 3.5cm x 3cm and is in good condition with signs of use over the years. A great little brewania item and a great curio.
For more information about codd bottles and their openers visit my blog site.