First, let's address the source for the introduction of saw teeth, and that is Gaddis, who covers the development of the model 18 in pretty good detail.

Saw teeth showed up fairly quickly on other models i.e. the 14, 15, and 16, probably '64 anyway. I will try a post a few photos of some early examples.

I couldn't say for certain when they showed up on model 1's and 5's, but I would say sometime in 1965 as a reasonable time frame. I need to look thru some notes and photos when time permits.