Apparently the Mark VIII (aka Mark 8) was a joint effort by the United States and United Kingdom. It was referred to as the Liberty or The International, and was intended to fight in World War One (The Great War), but production delays prevented that.
U.S. Army Ordinance Department.
Images are dated February 1919. Notice the access door has a large porthole type window.
USA Ordinance Department.
There is also a large porthole window on the back of the castle tower (turret).
USA Ordinance photo, February 1919.
U.S. Mark VIIIs were assembled in factories in Connecticut (Locomobile Company of America), Ohio (Parish and Bingham Company) and Illinois (Rock Island Arsenal). They were also built in the U.K., by the North British Locomotive Company, William Beardmore and Company, and Metropolitan.
USA Ordinance Department photo.
These photos are dated 1918, and show the first Locomobile built Mark-8 undergoing testing (like mowing down trees).
USA Ordinance Department photo.
USA Ordinance Department photo by N. Nazarnick.
This photo was taken towards the end of 1918, it is marked as being received by the USA Ordinance Department on 24JAN1919, a water crossing test just outside Bridgeport, Connecticut.
USA Ordinance Department photo by N. Nazarnick.
Locomobile Mark-8 completing a successful hill climb. The open hatches reveal the location of the driver.
USA Ordinance Department photo by N. Nazarnick.
10MAY2021: 