Does anyone know how this trick is done? Thanks

Good afternoon, I saw a card magic effect on YouTube, originally called "Circle of Fire," created by Paul Curry. It's super visual and really eye-catching because of the staging, even more so than the effect itself. In the video, a card is basically forced, and flash paper is placed between two coins, balanced on top of a small glass bottle—specifically, Morgan dollars. The effect is performed once for the spectator: the flash paper is burned, and the unburnt part between the two coins is removed, showing nothing written on it. But when the process is repeated, and another piece of flash paper is placed between the two coins, the performer makes a magic gesture, passing the spectator's forced card over the coins several times, seemingly transferring its identity. After lighting the flash paper again... the coins are separated, and now the index and suit of the card appear printed on the part of the flash paper that didn't burn because it was nestled between the two coins. Could an expert please explain how the index and suit of the forced card are transferred to the flash paper? Or is the secret in a Morgan dollar shell? Many thanks.