Quote Originally Posted by JimmyHAD View Post
My idea that the small notches may have been there to hold one end of the blade in a fixture for some step in the manufacturing process comes from my limited experience with milling machines and lathes when building tattoo machines. As anyone who has messed with mills/lathes knows, you frequently have to fashion jigs/fixtures to hold work securely.

Looking at the evolution of the straight razor blade and scales it seems to me that the notch evolved along with the distinct tang, longer monkey tail, slight curve to the scales. IOW, they found a purpose for it. Whether it was to more easily get around the nostrils when trimming a mustache, as I believe, or to allow the razor to be opened with one hand is something we'll probably never know.
Of all the serious answers in this thread I like this one.

If I watch the videos of Dovo or TI modern shops they now use heavy
powered hammer to forge the shape in one or two blows. In some
cases two blades at a time followed by a cutter step to remove
the razor from the raw stock.

If I was building tools to hammer out a blade I would like to be able
to have an index mark to push the object into so that the blade
would line up for the next tool after reheating...

That index notch would have evolved and been styled to
what we see today... Or it would have been ground off.

While we chart the progression of the notch over time
we might also track the availability of heavy forge hammers.
Of value in tracking the forge hammer tools might be
a bit of info on how well the razor shaves. My emotions
want steel that has been hammered a lot and has almost
a shot peening effect including the time that it is necessary
to remove scale and decarborized steel in the finishing
steps.l