It's either the 2 Card Monte or The Card switch in closed hands..
There's a booklet/lecture notes from a street magician but I cant remember where this was originally written about.

Can anyone help?

Thank you!

If you just replay the performance over and over... you'd be able to learn it

2 card Monte uses a DF and a DB card. It is found in many beginners magic sets.
The effect David Blaine did on TV is not 2 Card Monte. That was just his presentation for Eddie Fechter's Be Honest, What is it?

Years ago I purchased an item called THE MYSTERY ADDER> IT was a cardboard sleeve that had a window with about 5-6 vertical 6 digit #s to be added one by one. No-one and I mean no-one ever added these up correctly. It was an off-brown color and had a small picture of a swami on the front. Can anyone tell me if this is still around? I am also looking for an item called Mental Choice. Three playing cards with colors printed on the face. The pen naming the color has broken. I need the whole shebang or a way to replace the gimmicked pen that predicts the chosen color.

Didn't Ellusionist has a project that teaches this trick using Blaine in the advertisement years ago?