I photographed these M1918 155mm Howitzer variants at Fort Lewis and Camp Shelby.
The A1 advancement replaced the wooden wheels with rubber wheels for efficient road travel.
The M1918 is a U.S.-manufactured version based on the French Schneider 155mm Howitzer
M1918 155mm Howitzer and Caisson
I now think there may have been some confusion as to whether the Caisson and the Howitzer were meant to be displayed together or if they are two completely separate artifacts.