I like the routine, except for the ending. It's a little weak. Turning the Chinese coin back to silver - miraculous! Pulling the other silver coins out of your pocket - not so much.
Pants pockets aren't terribly miraculous - you can hide a lot of things in your pants! But a shirt pocket visibly changes shape when there's weight in it and changes again when it's empty. Not knowing the details of your routine, you might need to use a gimmicked shirt, but it would make for a stronger routine. If that doesn't work for you, using a pouch that can be displayed as empty at the start and end of the routine shows clearly that you're "changing" the coins, rather than "exchanging" them. Again, don't know the routine's details, but there are gimmicked pouches if you need to stash coins in a bag that's supposed to appear empty.
The patter is good, but use just a little less of it, or stretch out the timing a skosh. Give people a chance to absorb the little miracles you execute during the routine and it will give it more power. Pause the patter for a moment just as a change occurs and use hand gestures to draw the spectator's attention right where you want it, at your fingers. There's a natural tendency, even when listening to a magician who you know is going to try and pull a fast one, to look into a speaker's eyes when they're THISCLOSE to you and directly facing you while they talk. If you talk over a change, they're paying more attention to the words you're saying and it robs the effect of some of the available attention, thus sapping it of some of the power it has. The moment you stop talking and the fingers are in motion, especially if you time it well, their eyes and their focus will shoot to the hands right at the moment you make the miracle happen - that hits with more impact. Then you continue the speech, weaving the tale and mesmerizing the listener.
Getting them accustomed to looking for your hands when you stop speaking also means you're training them to look at your eyes when you are speaking, thus allowing for some sweet misdirection! I have a routine I do where my spectator is holding a packet of cards and counting them. Their attention is so focused on that act of counting cards, I could march a parade band behind me in full regalia and they wouldn't even know. It's simple, it's subtle, but it allows you to do oh so much while going unseen. You get a chance to steer your audience's focus, TAKE IT. Turn them into passengers in their own bodies!
Something cheesy like a smoke effect or fire effect would really punch this routine up a little, depending on how you wanted to play it, and would completely rivet their attention precisely where and when you want it. There's a reason such gadgets are popular.