Die Kunst zu Zaubern by Alexander Adrion (German book) Page 206
Personal Comment: Consider this a free trick. As there is nothing left to hide here. If you do exactly as I did in the video you'll end up on the Ace of Hearts. It's self working, it's mathematical... it's not bad. I took the German title for this trick as I am working from the German book. I got no original material. So if anybody knows... Shoot!