A friend of mine got this from his father a while back. It came from West Virginia back in the 60’s or 70’s.
There are four holes with a flap and peg that can pivot to fit into any of them.

The end has three drilled tubes, that have had corks inserted into them. All of these holes have bottoms, they do not go anywhere, to lead one to believe this could be a musical instrument.

Although the photo is fuzzy, you can see there are two holes in the side as well. The one on the right has a cork broken off in it. The one that is open and exposed, has a bottom. It does not go anywhere.

Does anyone know what this may be?

There are those that are not believing that this is a Muzzleloader block. Here, for those doubters, are the instructions, for this exact object.