I'd send Kim a nice letter and include the fact that the "second" shipping of the RSS4, with the "added S", could have been YEARS later than its' initial shipping date. It could have set in a gun shop for quite some time prior to being sold. The owner might have "sat on it" for a while prior to testing and decided to return the gun to Ruger for repair work. Who knows?
I'd certainly try my best to learn the facts.
flatgate
PS One other question to ask. Did the initial invoice list the Single-Six at the standard Distributor price or was it "discounted"? Same question applies if a "second" ship date is found.