This is a small leather powder or shot bottle based on a surviving example from the 18th century.

A powder bottle was used to carry gun powder for firelock weapons in the 17th and 18th centuries. It contained a small amount of gun powder to prime the pan on the lock ready for firing.

This one has a wooden stopper that fits snuggly into the top of the flask.

It is approx 3" wide and 6" high.