Looks like an effective way to clean the more valuable finds without damage.
For all my badly red-brown stained modern clad that I want to put back into circulation, I use the "soy sauce soak". Using inexpensive soy sauce which is acidic and salty, just soak your nickels, clad dimes and quarters for a few hours. They come out looking like money again after rinsing and wiping 'em off. Spray a little WD-40 on 'em after cleaning so they stay silver colored, and they're good to go. ^_^