1899 US Bayonet - Spanish American War (9D)

Listed is an 1899 United States military Bayonet that was used during the Spanish American War era. I can find three markings. One the handle t is a "9D" surrounded by a "Keystone" symbol. On one side of the blade t are the letters "US" and on the other side is the date "1899". Other than being tarnished with age, I consider it to be in excellent condition. Buyer pays $6.50 shipping in the USA.