I'm referring to the Techs made with the triangular slots made from what, the late 30's to just after WWII. I haven't compared them closely but they seem awfully similar. I have never seen an English Flat Bottom Tech in person much less shaved with one but I've had my War era Tech for many years. I find it slightly more aggressive than my ball end Techs - one from 1946 based on the blade codes in the box and the other a 1961.