Harmonica Plate - GRPO 12707 - Public Domain image, National Parks Gallery

Copper alloy harmonica plate with ten rectangular reed slots, and an equal number of corresponding reed attachment holes arranged in a straight line along one greater margin. This example recovered during archeological investigations at Fort Charlotte is thought to be from the early 19th century, as the first patents for were issued for mouth organs or harmonicas were issued in Germany in 1822. It measures 10.0 cm long, 2.5 cm wide, and 1.0 cm thick.