Two different types of percussion caps were recovered during the 1999 excavations at Second Fort Crawford in Prairie du Chien, Wisconsin.
The first type , found in the Enlisted Men’s Quarters, is a cap with ribbed or corrugated sides known as a “common cap” (left), sometimes called “pistol cap” due to its smaller size and lighter ignition charge which was more suitable for pistol or small rifle operation (Gooding 1975). The common cap recovered at the fort has extreme firing distortion.
The second type of percussion cap recovered is a “Top Hat”, also called the “military” or “musket” cap (right). This type of cap was developed to be easily handled by soldiers wearing gloves, however, these were not exclusively military issue (Gooding 1966). The “Top Hat” cap recovered at the fort was found in the Officers’ Quarters and exhibits slight splitting of the sides from firing.
Gooding, S. James
1966 The Percussion Primer. The Canadian Journal of Arms Collecting 4(4): 127-129.
1975 Pellet, Tubes, and Caps: The Percussion Primer, Part II. The Canadian Journal of Arms Collecting 13(1): 107-125.