No, there's no noticeable difference in the skin surface of my hands. Over years of practice, serious coin workers do develop substantial hand muscle strength and joint flexibility but that's not visually noticeable. It's also just a byproduct of practice and not needed for most of what we do. The key physical ability isn't applying force, it's actually enhanced sensitivity. I can feel precisely where the coins are and feel how the weight is shifting as they move. This sensitivity enables precise control which is really the key thing.