It's for catching fish farts, which are then sold to spirit level manufacturers for the bubbles in their spirit levels. Anyone would know that fish farts produce the most accurate bubbles ever put into a spirit level.
Are you interested in Old Tools and Tool Collecting? Want to learn more about tools, and meet some great people who have the same interests? Please take a minute to check out the Mid-West Tool Collectors Web Site at this link: www.mwtca.org.
Hitch a ride on the Time Machine and you can go revisit the factory when it was made. The other tool is a Stanley 12 measuring tape, although we use 25 and 30 footers nowadays.