I know there's been discussion over the various incarnations of the Stanley plane iron on the Old Tools List (did you know Stanley Australia briefly sold HSS irons? Fun fact o' the day), but finding it is another matter. Best bet might be to try a site-specific Google of the archive and expect to spend some time. If we don't hear from you again in a month, we'll send search parties...
Personally I haven't seen differences in the pre SW (Rule & Level) and the SW blades, in terms of apparent structure (when grinding etc). I understand the SW mark was really a sub-brand marketing device relating to when the 2 companies merged around 1922 (I think?) and didn't imply specific technical changes. I mean the mark alone may not denote tech / spec differences, I don't mean there were none during the life of that mark.
Jim here found a good ID site for old US Stanleys a while ago, but it's somewhere in one of his boot fair threads and I can't find it.
Jim - find it again please??