DL20K - Thanks! Yeah, these really are of great historical significance, yet they are really overlooked by collectors.
Amazon99- Honestly, I don't have very much information about these. These are listed in the Krause Standard catalog of Spain, Portugal, and the New World that was released in 2003. Other than the little bit of information that listed there, I know little about these.
A funny story about my coin is that I bought it from my dealer for $3 since neither he nor I had any idea what it was. He just figured that it was some medieval coin that he wouldn't be able to ID in a million years, so he gave me a good deal. Later I was browsing through my Standard catalog of Spain, Portugal, and the New world, I flipped to a page at random, and I saw a sketch of a very old 16th century coin that I swore looked oddly familiar.