Guano,
Sorry you didn't get the answer you were looking for. It wasn't for lack of interest. When I saw your question I, too, went to the USFA web site in search of an answer. I also went through all of my old USFA catalogs but couldn't come up with anything difinitive. I own several USFA's but, as luck would have it, no Rodeos.
If I had to hazard a guess, I would say that the markings on your gun are new - I don't recall ever seeing them on the Rodeos that I have handled. Then again, I haven't handled all that many.
CJF