Depending of which data one is reading: the 2 dot stamped blade began in 75 and the small brass handle pins ran 2,4 then 3, in quick order. Then settling on the large 3 brass pins in 76. (Bill Keys) I've discussed this with him and Joe Houser.
Other respected collectors say the 2 dots began in 1974. Another collector says the 2 dots began in 1976. I respect all of these gents so, I take the middle road on this date. DM