Take it out of the flip. Weigh it. Genuine steel cent: 2.70 grams. 950 copper cent: 3.11 grams. Copper plated zinc cent: 2.50 grams. It is missing all the visual indicators of a dime planchette struck by cent dies, so I will discount the possibility.
My guess is a genuine 1956D that has been plated. Depending on the plating metal, and the plating thickness (think in terms of microinches), the weight could be as high as 3.20 grams. Do an internet search on making silver pennies, making gold pennies, and other such terms. You might be surprised what we did in grade school 45 - 50 years ago.
Time for more coffee. I have a 2 for 1 coupon from Dutch Bros.