This is a fine example of an antique pharmacy tool-of-the-trade known as a pill machine (often mistakenly labeled as a "pill roller").
It is constructed of what appears to be walnut with a brass mechanism.
The early pharmacist slid the top paddle over the matching base, cutting a dough-like, medicinal mixture into cylindrical tubes. The medicinal tubes were then placed on a pill tile and were measured and cut with a pill knife to sizes providing the proper dosages.
The base measures 12" L x 7.25" W. The paddle measures nearly 16 inches long. Condition is very good with the expected wear commensurate with age and use. Sports a fabulous patina!