Nitpicking technicality: An implication of Newton's Third Law is that it is impossible to "strike a coin on only one side". If a die comes down onto a coin blank and there is no other die to catch it and force the compression of metal, then a coin cannot be made. It's the numismatic equivalent of a strike in baseball: a swing and a miss, and nothing actually happens. If it's a "coin", or a coin-like object made in the same fashion as a coin, then it must have been struck on both sides.
So rather, it is best to describe it as a "coin that is blank on one side" or to give it its fancy-numismatist Latin name, "uniface"; the other side is made using either a specially prepared blank die, or (in the case of items like the Gheens token posted above) a plain anvil-like surface.
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