For the dating I follow Farrington (2012), no. 1.32 and p. 110-1 note 237; a central victory were Theogenes' Olympic victories in 480 and 476 in boxing respectively pankration, attested in Paus. 6.6.5. Syll.³ 36A = IAG 21 as well as Paus. 6.11.5 attest however also 10 Isthmian, 3 Pythian and 9 Nemean victories, mostly boxing, as well as a dolichon victory at the Hekatomboia of Argos. Pausanias specifically adds a victory at Phthia in Thessalia also for the dolichos.
The inscription says he was unbeaten for 22 years and had 1300 victories; Pausanias 6.11.5 speaks of 1400 victories.
Klee (1918: 89-91) posits his Isthmian victories between 490 and 474 (winning them all), with perhaps 486 being the attested double victory in both boxing and pankration, though he bases this on IvO 153 of which I am not certain it pertains to Theogenes - Farrington suggests the last Isthmian victory of Theogenes was his double victory, which may have been as late as 470; Klee (1918: 70) puts the Pythian victories at 482, 478 and 474; Klee (1918: 99-101) posits the Nemean victories from 489 till 473, winning every contest in boxing. - PK
NB: Moretti (1957), nos. 201 and 215 wrongly state that the father's name is Timosthenes (the sources clearly say Timoxenos). - CT