Here's a wonderful coin concealment that you may want to add to your repertoire. It's called the Downs Palm, popularized by T. Nelson Downs. It looks like this if you want to actually produce a coin, which, I happen to see one right over here. We can pluck it out of the air. The Downs Palm is a palm that utilizes the thumb and the base of the bone for the pointer finger, which is right there. Just have the coin in that position, so if you can get to that position you're good to go. You should be able to shake hands and the coin will not fall out. From the front this looks very, very natural. You can move your fingers and are free to do what you wish. You could play piano if you like, as long as you keep your thumb and your middle finger together.
You can then show the other side like this. You shouldn't be able to see the coin in that exchange. Once again from the front, keeping the middle finger and thumb together, move it over, opening. To make the coin appear is very, very simple. You come in with the middle finger. The middle finger goes to the bottom of the half dollar, or quarter, or whatever coin you're using. The pointer finger comes on top, pulls it out of that thumb crotch position of the Downs Palm, and then the thumb pumps it into view. The Downs Palm can also be used as a vanish. Here's how it looks, taking the coin and tossing it up into the air. You can make it appear once again by using the Downs Palm.
Here is an exposed view. Having the coin clipped between the middle finger and the pointer finger you're going to bring that coin slowly in, put the thumb crotch, which is right here, gripping it, releasing your grip as your fingers come out and your hand goes up. The Downs Palm.