During the early phases of the fighting of World War 1 (1914-1918), the Thomas B. Jeffery Company of Kenosha, Wisconsin (USA) became the recipient of a Canadian military armored car requirement. The Army sought to establish a new battery of machine gun-armed and armored trucks to help the Allies break the stout German defenses across Europe. The Jeffery Company was already producing the successful four-wheel drive "Jeffery Quad" at the commercial level and this chassis, and its standard drive, were selected by the Canadians for a special conversion process. The armored steel plating was provided for by the Bethlehem Steel Company of Pennsylvania and this combined work gave rise to what became the "Jeffery Armored Car".
Wealthy Canadian Businessman John C. Eaton lent the project capital and Jeffery Company superintendent Jerry De Cou drew up the export-minded design. For the Canadians the result was a single-turret, fully-armored war machine with four-wheeled drive arrangement. Steering could be accomplished from the front and rear of the vehicle - this allowed the car to simply drive away from danger without having to turn completely around. The cylindrical turret was centrally-located on the hull roof line and armored cupolas were featured fore and aft of it for the drivers. The engine remained in its typical forward placement and consisted of a single 4-cylinder unit allowing the heavy vehicle to reach road speeds of 20 miles-per-hour on prepared surfaces.
Dimensions included a running length of 18 feet, a beam of 6.4 feet and a height of 8 feet. Ground clearance was excellent due to its truck roots but, as with other World War 1 armored cars and trucks, the commercially-minded vehicle lacked strong cross-country mobility and performance due to the added weight of the armor and armament as well as relatively weak drive power. The operating crew numbered four and armament was centered on up to four machine guns of either Benet-Mercier or Vickers design. Beyond the turret emplacement, there were rear-mounted side sponsons containing the armament. Hinged entry-exit hatches were set all about the hull superstructure - at the vehicle sides, top, and at its rear.
Production of what became fifty total vehicles took place during 1915 and into 1916 in both the United States and Canada. In the latter this was handled by Canada Cycle & Motor Company Limited which already held experience in the production of "Russell" trucks so this led to some of the stock to be referred to as "Russell Armored Cars" for their part in the story. In Canadian Army service, the trucks were used to form the "Eaton Motor Machine Gun Battery" and were shipped to Europe to take part in the fighting as soon as September of 1915. However, the once-fluid war was no more by the end of 1914 and the trucks arrived with no useful battlefield role in trench warfare - essentially ending their wartime service in storage. For all their expense, training and work involved the vehicles did not see combat in The Great War.
Beyond Canadian military service, the car was also operated in varying numbers by the United States and Britain. In the former, American General John Pershing's "Pancho Villa Expedition" (1916-1917) trained with the type (as "Armored Car No.1") during 1916. These were similar in design to the Canadian forms save for a two-turret armament arrangement (one center, one aft) and were completed at the Rock Island Arsenal. In the latter, they were operated as part of British India Command mainly for local security at the colonial level. Some were also operated by the British in Ireland for local security.