I did see the following from Wikipedia:
Unlike later Jewish coinage, Yehud coins depict living creatures, flowers and even human beings, in contravention of the Second Commandment “Thou shalt not make for thyself a sculptured image or any likeness” (Exodus 20:4). During the First Temple period figural art was frequently used, such as the cherubim over the Ark of the Covenant, the twelve oxen that supported the giant laver in front of Solomon’s Temple, etc. Thus, it is likely that the Yehud coins are continuing the use of figural art from the previous period. The prohibition against graven images in Exodus was probably seen as relating only to idolatrous images rather than the purely decorative. Depictions on the coinage include imagery borrowed from other cultures, such as the Athenian Owl, mythological creatures, and perhaps even images of Jewish rulers.** One coin depicts an enthroned deity, claimed by some experts to be Yahweh, while this is disputed by others. It has been suggested recently that this coin was actually minted in Samaria and depicts Samarian Yahweh.**
So yes, it could be possible that this 4th century BC coin is a depiction of Yhwh (or rather, Yhw - which is what the inscription says), but we are not totally sure. At least, the winged wheel seems to evoke for some people the vision of Ezekiel. We aren’t even sure who minted the coin in question: whether it was the Jews themselves or the Persian authorities of Yehud. I’ve seen a number of alternative ideas, one of which is to the effect that this is a syncretistic, general template of a god (perhaps a solar deity) easily comprehensible to many people in the western part of the Persian Empire with the name of the Jewish God tacked on it.
You have to remember that early in their history, the Israelites seem to have had a pretty lax interpretation of the commandment against graven images. It seems that what is really forbidden is more the depiction of the Deity Himself, although as mentioned this rule is not always followed. Aniconism (the use of an abstract symbol or an empty space to symbolically represent a given deity) wasn’t unique to the Israelites: it was a common feature of West Semitic religions in general. The active prohibition against idols however was unique to them. Quoting myself for a moment from another thread:
Scholars generally define two types of aniconism, both related to one another: material aniconism, which refrains from using effigies, but rather makes use of abstract images or symbols - like poles ('asherah) or standing stones (maṣṣeboth) to symbolize the divine (cf. Greek xoanon and the Hindu lingam), and empty space aniconism, which makes use of an empty space as a symbol for the god’s presence. Genuine West Semitic (Canaanite) religion in general was aniconic: for most West Semitic religions, a sacred place meant an open-air temenos with stelae. (There were exceptions to this, particularly in areas like cities, where we have evidence of iconic cults.) Now there are some cultures, like the Phoenicians who favored the ‘sacred emptiness’-type of aniconism: very often what was chosen was the image of an empty throne or animals like bulls, where the deity is envisioned to sit or ride upon.
West Semitic aniconism wasn’t of the “thou shalt not make any graven image” type, as the Israelite version was: while the norm amongst the majority was to use abstract symbols, there was nothing which prevented the use of actual effigies or figurines to represent gods. It was not a question of prohibition, but of preference and mentality.
We could see that the early Hebrews originally held the former, although they would also eventually adopt the latter. Within the Old Testament we often hear of maṣṣeboth being set up in commemoration of some event (usually a divine revelation) or in memory of someone. On at least four occasions, Jacob sets up a standing stone in connection with certain events of his life: the most well-known is, of course, after he receives the vision of the stairway reaching to heaven in Luz/Bethel (Genesis 28:18). In Genesis 31 (v. 45-54), Jacob erects another stone, as well as a mound, as a witness of his decision to leave Laban. After his return to Bethel, God appears again to Jacob, and once more, Jacob erects yet another maṣṣebah in memory of this (Genesis 35:14-15). Not too long after this event, Rachel dies and Jacob sets up one last stone in his wife’s grave (35:20). Also, God’s covenant with Israel through Moses was represented by twelve maṣṣeboth erected at the foot of Mount Sinai, one stone for each tribe (Exodus 24:4). Finally, the book of Joshua also records a number of times that such monuments were erected pointing to the power of God: in Joshua 4:20-24 for example, Joshua sets up twelve stones taken from the Jordan in memory of Israel’s miraculous crossing of the river. Near the end of his life, after Joshua challenged the Israelites to serve God, he takes a large stone and sets it “under the oak that was in the sanctuary of Yhwh” as a witness against them should they deny the Lord (24:25-27).