The only differences is the stamp of course. SA versions did have the hex butt cap ( there were a few US hex butt caps made when CRK moved to the US and had some left over ). In the beginning, some were made with D2 steel, later they were made with A2 steel. CRK switched from D2 to A2 and vise versa every once in awhile when the other steel was not available, but they are not marked and they do not know when this occured. I am sure its stated on the BD cards, but other than this, I know of no way of knowing. ALL blanks of the OPR were rough ground in SA ( wether made in SA or US ). This is the reason they were recently discontinued. The gentleman that ground them retired, so rather than grind them here in the US and raise the cost quite a bit, CRK decided to discontinue them. As far as years of certain models go, look at my CRK timeline in the stickey, this may help you furthur. Enjoy !