I collect coins, and there's always debates about what a coin is.

For those who don't know, a coin is usually defined as an object with legal tender status somewhere; as opposed to a token that has a face value but is issued by a non-state actor; and a medal, which is anything that looks like a coin but doesn't have any face value.

Now, aside from the expected debate over what is and isn't a state, there's also the issue of NIFC (not intended for circulation) coins. Many mints sell coins that are legal tender, but are never put into circulation, some people (often those that could be characterised as "old school") take the position that as these aren't intended to be used as legal tender, they aren't really coins.

It doesn't help that there are tiny island nations like Niue and Samoa that will basically let companies make anything legal tender if they pay them. This leads to the rather silly situation where a batarang, and a literal statue of hogwarts, are technically "coins". (I've been told this is done as a import tariff dodge as the USA doesn't charge import taxes on coins)