Mark,
My guess is a late 1971 or 1972 with the straight accent running through the riser. I believe in 1974 they switched to the curve accent in riser.
Now remember the “Knife Edge” has absolutely nothing to do with the curves on limbs or accents but it is found only on the early 1960 model bows and that was where the sight window was sanded over sort of like the looks of a “Butter knife “ and I’m thinking 1962 but don’t quote me on that year but it was early 1960’s. Now if memory serves me correctly it was stopped just to help speed up the process in making the bows from what I have read and asked .
Larry Hatfield will answer any questions you throw at him but give him time to reply back to you.
I have one knife edge and it was Gifted to me and it’s the Diablo shown below. If you aren’t sure look closely at the curve on the belly side of sight window.
“See the curved area that runs up about 4 or 5”? That is the knife edge from my understanding and made it a bit easier looking down the arrow with the 90 degree edge curved over.
Hope that makes sense cause I’m not the best teacher lol.