Brass cone and wooden handle
Brass cone shaped top with a pivoting ‘knife’. The cone shows signs of rotational wear.
the knife is not sharp and probably never was.
The blade folds into the cone and reveals just a sliver of the back.
It looks like it might be some sort of a cork reamer for a barrel, but that would not explain the pivoting blade.
If you think you know what this tool is then drop me a line.