 Stephen's period determination supersedes previously reported results by Vincenzo Zappalà (1985; 12 h), Federico Manzini (2007; 12 h) and René Roy (2009; 22.5 h) ().According to the surveys carried out by the Infrared Astronomical Satellite IRAS, the Japanese Akari satellite, and NASA's Wide-field Infrared Survey Explorer with its subsequent NEOWISE mission, "Antilochus" measures between 101.62 and 111.69 kilometers in diameter and its surface has an albedo between 0.053 and 0.063.The "Collaborative Asteroid Lightcurve Link" adopts the results obtained by IRAS, that is, an albedo of 0.0633 and a diameter of 101.62 kilometers, with Pravec's revised absolute magnitude of 8.59.