One of the most interesting early Greek inscriptions involving a Jew/Judaean is the so-called “Moschos inscription” (or “Moschus inscription”), a record of a manumission found in 1952 during excavations at Oropos north of Athens. The inscription was recovered from the Amphiareion, a shrine to the hero Amphiaraos.  The inscription itself bears no date but is generally assigned to the first half of the third century BCE, which would make it among the earliest Greek inscriptions to mention an ΙΟΥΔΑΙΟΣ in the singular. I was having a hard time locating an image of the inscription online, but I recalled having scanned the publication some time ago. I was able to find the scan and have posted it here:

Inscription of Moschos Ioudaios from Oropos, SEG 15.293; image source: Markellos Mitsos, Archaiologike Ephemeris (1952), 195.

The first lines establish that Moschos is being freed by his owner. Then follows a list of the names of witnesses to the manumission. The most interesting portion begins midway through line 11:

. . . Μόσχος Μοσχίωνος Ἰουδαῖος
ἐνύπνιον ἰδὼν προστάξαντος τοῦ θεοῦ
Ἀμφιαράου καὶ τῆς Ὑγείας καθ’ ἃ συνέταξε
ὁ Ἀμφιάραος καὶ ἡ Ὑγίεια ἐν στήληι γράψαντα
ἀναθεῖναι πρὸς τῶι βωμῶι

. . . Moschos (son) of Moschion, an ioudaios,
set up (this stele) having seen a dream of the god
Amphiaraos and of Hygeia, in accordance with what
Amphiaraos and Hygeia commanded, having written (it) on a stele,
to set it up at the altar.

The inscription is of course famous because Moschos identified as an ΙΟΥΔΑΙΟΣ but at the same time set up a stele to Greek gods after having been visited by those gods in a dream (perhaps the result of deliberate incubation at the temple). Both Moschos and his father (Moschion) had good Greek names (both names mean “calf”), and Moschos is visited by Greek gods, but he continues to identify as an ioudaios. It is not possible to tell whether this identification means that Moschos also worshipped the ethnic god of Judaea whose temple was located in Jerusalem. Typically, we assume that ancient people who identify as ioudaioi venerated only the god at the temple in Jerusalem, but the evidence of people like Moschos suggests that this was not always the case. The inscription also problematizes the idea of the designation ioudaios as a “religious” signifier.

Some further reading on the inscription is given below. The full Greek text of the inscription can be viewed online at the relevant PHI entry.

Bibliography:

Cohen, Shaye D.  The Beginnings of Jewishness: Boundaries, Varieties, Uncertainties. Berkeley: University of California Press, 1999. Pages 96-98.

Fredriksen, Paula. “How Jewish Is God? Divine Ethnicity in Paul’s Theology.” Journal of Biblical Literature 137 (2018), 193-212 [Only mentions Moschos in passing in a footnote but provides excellent context for thinking about the inscription.]

Mitsos, M. Archaiologike Ephemeris (1952), 194-196.

Noy, David et al. (eds.), Inscriptiones Judaicae Orientis, Volume I: Eastern Europe. Tübingen: Mohr Siebeck, 2004. Pages 177-180 [This volume contains an extensive bibliography of earlier work on the inscription.]