This is a sweet, lovingly crafted old handmade 15 puzzle game, last quarter of the 19th century I believe, and found in Chester County, Pennsylvania. The game is played by removing the blank square and mixing up the other numbered squares, then sliding them to get them back in order 1-15.
The framework is held together with twelve handmade nails with irregular rectangular heads. The squares are hand numbered in ink, as is the top edge of the frame (1 to 4) and them a 5 at top left. I believe the wood is walnut but am not entirely certain.
3 15/16" x 4 1/16" x 15/16" deep and in great antique condition.