By the time surveyors returned in 1905 and again in 1937, it was recorded with hachuring, the fine radiating lines used on older maps to indicate raised ground, and the measured diameter had grown slightly, to around twenty metres, likely reflecting more careful observation rather than any change to the mound itself.

What stands on that slope is a ring barrow, a type of prehistoric burial monument consisting of a low earthen mound enclosed by a shallow surrounding ditch, known as a fosse. Ring barrows are found across Ireland and Britain and are generally associated with the Bronze Age, though their precise date and function vary from site to site. The Cooles example measures approximately twenty-three metres north to south and eighteen metres east to west, making it a modest but legible example of the type. Its enclosing fosse survives to a depth of around a quarter of a metre, shallow enough to be easily missed underfoot. The southern edge of the mound has been clipped by a field fence at some point, a reminder that working farmland and ancient monuments have long shared the same ground with little ceremony.