I recently saw some $1 notes (forgot the series or if they were FRN or Silver Certificates) however here is the gist of my question. One was printed with an "R" and the other with an "S". As I recall the "R" was valued the higher. Is either of these notes special for any reason and the price was $10 and $15.
What are these notes? Dealer says that they were tests of how different paper would stand up in circulation. Any thoughts?