A retoucher-hammerstone decorated with incised notches on its sides was found on the ground on Monte Alto, in the Alban Hills, just south of Rome. Macroscopic and microscopic (optical microscopy and SEM) analyses have made it possible to reconstruct the types and chronology of human intervention on the pebble, while a morphological, stylistic and micromorphological study of the notches revealed that they were made over time using more than one kind of cutting edge, possibly at the end of the Pleistocene. The definition of notational artifact could therefore apply to this object, making it one of the few known cases of the kind in the world prehistoric record. Moreover, it displays all the features theorized in literature for the validation of lunar calendars. This could have significant implications for the reconstruction of the cognitive and mathematical ability of Homo sapiens in prehistoric times.