There is, surprisingly, very little epigraphic evidence for the revolt of Carausius and Allectus. There is a single known inscription from Britain from the ten year hiatus of the British Empire which should be contrasted with the 20+ known inscriptions from Britain during the Gallic Empire (260-74AD). However, set against this the decline in the "epigraphic habit" in the late third century must also play a part.
The sole inscription of Carausius, a mile stone, has survived because it was up ended and reused. Found in 1891 on the bed of the River Peterill about one mile south of Carlisle the re-use has been reconstructed to be by one of two potential emperors, Constantius Chlorus (as Caesar) or Constantine I (as Caesar). The diagnostic part of the text is, unfortunately, damaged. There is a third inscription, wholly erased (Allectan, eradicated totally as it would have been seen even when the stone was turned upside down???), in the centre of the stone.
The milestone is important as it is the only epigraphic evidence for the full name of Carausius as it reads M AVR MAVS CARAVSIO.
The reference for the monument is RIB 2290-2.