I just got two RCA 6V6 black plates for $9.99 each from ebay. If you search for RCA Black black plates they cost a fortune. But if you look for FoMoCo (FOrd MOtor COmpany) radio tubes, they can be be had cheap. Evidently old car buffs are not into jacking up the prices for guitarists yet. They are branded FoMoCo, but have the etched stop sign - real deal RCA. Be careful: Ford used Sylvania, GE, and other brands, too.