Originally Posted by Kopsis

Ah ... for NW you're probably out of luck on silver ano. Even in black, 50t NW is scarce. If you want to do this right, find an industrial anodizing shop that will do walk-in piece-part work. They can strip off the black ano and apply sliver/clear. It may cost a bit, but you won't risk screwing up the metallurgy with caustic chemicals.