CALIBER REVOLVER' on the end instead of '.22 CALIBER REVOLVER'.
In the 560xxx to 566xxx range the SC6 box started appearing with '.22 W.M.R.
That being said, the maker of Ruger's two piece boxes also made a printing error, and it just happened to occur at about the same time the SC6M were produced. The only one that had been known was 555430, however we have no idea of the whereabouts of that revolver today. there were indeed at least 15 of the model SC6 Super Single-Six with 6-1/2' barrel shipped from the factory as.
