Kryptos

This is something I've been working on.  Truly, I haven't been working on it enough, but I'm collecting bits of information that do not require assumptions.  "Facts" I suppose, though I'm always wary of "facts" because "facts" != truth.  We know that the blue marked NVPVTT is plaintext BERLIN (at some point, at least, and in some way, at least) and we know this from Sanborn himself.  I also venture that the R in the ciphertext at the end may represent punctuation, as it has done in the previous ciphertext blocs.  Any ideas or approaches are more than welcome.