I haven't found another button quite like this one, and what a great one! Very early 20th century I'd think, and in a nice brass mount, which has kept it in great condition. What a perfect gift for your favorite farmer, or to pin proudly to your coveralls before heading out to the garden!
Some aging to the brass and to the back side, but still bright and shiny and in great shape. 1 1/2" in diameter.