To be honest I don't know - other than that's how is was described when I bought it. I'm more into straights and have never looked at all the data on models, dates, codes etc., but it was bought from a member on this site so I assumed he was correct. It is notched and there are no date codes that I can see (I used a loupe) so I gather from what you are saying is that the notched design was introduced in 1948 and date codes were stamped from quarter 3 in 1950, therefore it is not possible to date it more accurately than that.