This listing is for a Jennings Brothers Metal (maybe Pewter) trinket box in a deep gray color.  Marked on the bottom, Trademark J.B. Signifies The Best 521.  This piece measures about 4 inches long by 3.5 inches tall at highest point and 2.25 inches wide.  These trinket boxes were made by Jennings Brothers Manufacturing Company who operated a foundry and large manufacturing plant in Bridgeport, Connecticut from 1890 until the 1930s and specialized in clocks, silver plated tableware and pretty art metal items like I am offering.  This was called a dresser box or jewelry casket, with its high relief design of flowers with flowing curves and dates to about 1910-1920.

The metal is a white (non-ferrous) pot metal or spelter for easy low temperature casting, coated with various finishes, or left natural as with yours, a finish that the company called "French grey silver" although there's no actual silver in it. Others were anodized with gold or bronze or silver applied electrolytically.