well. i think the idea behind it is very good.
your handling needs to be improved though.
more to the effect-that "move" everybody in my school knows that trick. my brother who is ten can do it. I'm not discriminating it or anything, but i believe it is a slieght that has been passed around by friends for fun and stuff. perhaps a different sleight (im not that clued up on coin sleights so i can not offer anything) could do the trick.
and finally. i dont think it would work wit the audience signing the coin, if its done how i think it is.
good idea though
