To Be Or Not To Be? - Coin?

I don't think this would classify as a coin... unless it's spendable. I would consider this more of a decorative numismatic artifact

The answer to your question entirely depends on your definition of "coin".

If you accept "Coin" to be: "an object issued by a government and allocated a legal tender value in the currency of that government", then yes - it is a coin. So are the pyramid-coins of the Isle of Man, the geometric-solid-shaped coins of... I can't remember which country, and the acrylic coins of Congo.

If you change the definition to coins needing to be more or less round and more or less flat, or needing to be in a form that could be conveniently circulated as money if people chose to do so then no, this doesn't fit.

Is Niue a legitimate, coin-issuing government? The answer to that question seems to be "yes". Niue is a dependency of New Zealand, but New Zealand grants its three dependencies (the others being Cook Islands and Tokelau) considerable autonomy, including the right to issue their own coinages.

Of course, one thing that ought to be further investigated is whether or not the government of Niue actually authorized the issue of these particular coins. Rogue foreign mints have in the past issued "coins" which were never authorized by the government named on them, so therefore were never truly "coins". For this purpose they usually choose small, isolated, hard-to-verify countries (like Nauru and Niue) or countries in the middle of a civil war or otherwise with no functional recognized government (like Somalia).

Yes, I tend to draw the line at NCLT where the LT part is in somebody else's LT...

I'd love to see someone carrying a few of these in their pocket.

It's funny that they apparently copied the picture from the Mercury dime, which isn't even an actual rendition of Mercury.
(EDIT: looking carefully, they didn't - their version doesn't have the Phrygian cap, and, while it might be just my imagination, the face looks a little bit male-r. But I still somewhat doubt that this is actually enough of a difference to justify that the image on this coin is, in fact, "Mercury" rather than a misnamed and misplaced Liberty.)

Only different in shape - it isn't unlike the YAP coins made from tons of stone. I like it beautiful I would use it as a paperweight on my desk, and as a conversation piece. Very cool!

To qualify as a coin it must be technically legal tender, so bullion can qualify, even though it's not meant to circulate as money.

Additionally, I would argue that what allows us to identify a coin as a coin is generally its size, shape and material. Strictly in terms of appearance, the "ideal" coin is a small metal disc.

A metal cylinder does not qualify as a coin in my view. It's simply too far removed from what I consider to be the "ideal" shape.

There you go. I can out-think and out-philosophise the lot of you.