The Japanese word on both sides is "fan", which is not a native Japanese word but can instead transliterate directly from English: it can be used for both the English word "fan" (and any of the possible meanings of that English word) but also the English word "fun"... in the context of an amusement token, is probably better transliterated as "fun".
It may be an arcade token, in the same sense that an American arcade token would have been used. But it could also have been a pachinko token.
In Japan, gambling for money has long been illegal. However, there has been an equally-long loophole in the law that allows you to legally play a "game of skill" (not pure luck) and win prizes, rather than cash. Pachinko, in its original form, is a pinball-like game, thus involving "skill" rather than "luck". "Pachisuro" is a computerized digital version of the same game-style. This has led to the creation of two side-by-side groups of businesses: pachinko parlours, where pachinko and pachisuro games are played and prizes (in the form of balls) are awarded. These balls cannot be removed from the premises, but they can then be exchanged for "special prize tokens". Then, across the street from a pachinko parlour, you will find a convenient "token shop" where someone will happily "buy" those tokens off you in exchange for cash. Of course, if both the pachinko parlours and token shops just happen to be owned by the same organization (often a shady organization with links to the Yakuza organized crime gangs) then this amounts to "legal" gambling for money.
But the fact that the tokens are, indeed, intended specifically to leave the gambling premises does mean that many of them "leak" into the wider community and any tourists who venture into the pachinko alleys will likely bring home some tokens as a souvenir of their adventure. These then end up in the "random bucket of world coins" when the tourist's coin hoard is eventually disposed of.
Don't say "infinitely" when you mean "very"; otherwise, you'll have no word left when you want to talk about something really infinite. - C. S. Lewis