I've seen a few different CSB routines, but never seen one with this phase. I'm sure it's probably out there in some expensive book, but I thought I'd share my experience here.
When I was practicing my routine I accidentally opened my hand with the gimmick coins still together and showing the silver. Total disaster of a brain fart, lol, but then I realized I could make it part of the routine by showing that I now had 2 silver coins and the foreign coins had jumped back to my pocket.
I gave it a whirl next time I performed it and the response was really great. A loud, "What?!"
Then, put the foreign coins back in pocket and make them jump back into the hand as normal.
Kinda cool, thought I'd share. It worked really well for me.

Edit: I will add it might help it play well due to the fact that for this routine I act as though I'm never in complete control of what's happening. So it came as a "surprise" to me as well.

Great choice of performance "angle" for coin tricks which otherwise so easily devolve into "showing off".