In brief: Pretty but impractical.
Yes, C-Coin does what the sales video indicates; there is a color change of a coin, and it can be in the spectator's hand.
Yes, the gaff is what most magicians would guess it is.
Overall, the gaff looks pretty good, but the colored enamel / paint / coating is uneven. When the magic happens in a spectator's hand, they really look closely at it. In my brief trial, it was noticed 2 of 2 times. Maybe not that big a deal.
Dubious claim: "It resets immediately, so you're always ready to go."
Actually, it resets relatively quickly -- that is, if you're carrying (or have in your close-up kit) a special something that resets the coin for the color change. Or, it "resets immediately" if you have certain beverages in various states at hand.
Depending on ambient temperature of the area you're working, the time it takes for the gaffed coin to change color varies. Experiment, and try it out under various conditions so you won't be the one surprised by the color change.
Pretty effect, indeed. It could work for walk-around magic, under the right conditions. It will likely work okay in close-up magic circumstances.
For me, impractical. My "Coins-Across" works every time, regardless of the conditions. Sadly, this will get a home in my "good ideas" drawer.
Maybe snarky, but ... The Youtu.be link printed on the info card didn't work; I had to get the actual link from VI (which they sent in hours, great service!) But then, having the tutorial on Youtu.be frequently interrupted with ads, so the seller can make a few more cents on the view, is really low class. It seems like the maker could have a deal with Vanishing Inc. or Murphy's to present a commercial-free tutorial.