Mentioned in IG XII.5 608 lines 15 and 26, discussed in Schmidt, D. (1999), 'An Unusual Victory List from Keos: IGXII.5.608 and the Dating of Bacchylides', JHS 119, 67-85, p.70. I follow Farrington (2012), no. 1.40 and p. 113 notes 250 and 251. Farrington suggests Ioulis, perhaps Keos as the origin of the victor, since that is where the inscription, a victory list likely pertaining to Isthmian victors (Farrington (2012), p. 113 note 249), was found (from l. 17 onward it pertains to Nemean victories).
Farrington's note 250 pertains to Bacchylides Epinicia 1.155-7 and 2.4-10 also referring to Isthmian victories of a certain Argeios, perhaps both referring to the same victory, and perhaps the same Argeios as mentioned in the inscription. Farrington follows Bacchylides career dates to date the victories of Argeios. Note 251 follows up on this, saying that Bacchylides suggests a combat sports discipline for Argeios. Farrington suggests perhaps pale or pankration, pux (pugme) has also been reconstructed; in reality only the age categories are legible. - PK