The blazon can be found on the Basel town hall

It depicts two war axes that are crossed. The other flags depict banners of states of Switzerland, the one to the right is Wallis.

More pictures of the town hall

Wikimedia

Tomas Travel

Handelszeitung

It does not seem to depict a blazon of one of the Swiss cantons/states, as the banner cannot be found in the table of states (de)

What does, or did, it represent?