All credit to u/dctroll_ for the find and writeup. I decided to put some work in to upgrading the image, and here we are. (I particularly liked that it savored of “ligne claire")

Chesters Roman Fort, known as Cilurnum, was built around 124 AD as part of Hadrian’s Wall in northern Britain. It was an important cavalry fort designed to accommodate around 500 soldiers who helped control and defend the frontier. The first unit stationed there was the Ala Augusta, a cavalry regiment known for its bravery. During the 2nd century, the fort was rebuilt and different auxiliary units occupied it. Around 178–184 AD, the Second Asturians, a cavalry unit originally from northern Spain, arrived at Chesters and remained closely connected with the fort until the end of Roman rule.

As at all Roman forts in northern Britain, the period AD 180–250 was the heyday of both the fort and the sprawling civilian settlement (vicus) lying outside the walls, providing services and accommodation for soldiers and their families.

During the 3rd century, political and military problems across the Roman Empire caused changes to the army and the civilian settlement gradually declined. By the 4th century, the garrison was probably more locally based, although the Second Asturians may still have been present. Chesters probably remained occupied until the Roman administration of Britain ended in the early 5th century.

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