M7 Priest

The M7 Priest was an American designed Self Propelled Gun (SPG) that was primarily used by the British army. It earned its name from its interesting design, with the BMG mount making it look like a priest's pulpit.

IRL

The M7 started as a modified M3 Lee chassis that could hold a 105mm cannon, after American observation of the war found a need for SPG within their armored divisions. Lessons learned from the failed T19(TL;DR, a half track with a mortar) influenced the development of the vehicle as a dedicated tracked SPG. Later in the war, the vehicle was built on the M4 chassis with the adoption of the Sherman as the primary tank for the United States to ease logistics.

The British got their hands on some of the first vehicles, and while they found them to be decent enough vehicles, the 105mm Howitzer used seperate ammunition from other British guns, which complicated logistics. They saw reliable service in Africa and even post war, though they were replaced shortly after the Normandy landings with the QF-25 Pounder Howitzer and their own Deacon, converting most of the remaining vehicles into tugs and troop carriers.

In spite of these shortcomings and hiccups, the vehicle was solid, and served until the Korean war.