The horse trappings were found in the early nineteenth century at the Roman city of Castra Vetera near modern-day Xanten in the state of North Rhine-Westphalia.

The heightened military presence encouraged the development of a large city nearby that became the second largest settlement in the province of Germania Inferior.

Gaius Plinius Secundus, better known as Pliny the Elder, was a Roman historian, author and army commander in the reign of the Emperors Claudius and Nero.

One of the horse-trappings bears his name and reads: PLINIO PRAEF(ECTO) EQ(UITUM) ('while Pliny was Prefect of the cavalry').

This suggests that these horse-phalerae belonged to a cavalryman under his command when Pliny was stationed in Germania Inferior in approximately 50 AD.