On some brands of blades I have it says 1 and 2 on the sides and the other side says 3 and 4. I put the 1 and 2 on top but is it neccessary? What are the numbers for?
Since some blades don't have numbers, I figure numbers must not be overly important. That said, I believe the numbers are used for those in the medical and scientific fields for whatever reason they see fit, not shaving. Some folk use the numbers to keep track of their blade flipping.
I believe the numbers are to allow the user to flip/turn the blade per usage. While I don't think it makes a huge difference, I'll put the 1 in the upper left corner of the cap when loading; next day the 2; next day flip to 3, etc.
I think I believe I maybe (!) saw something once that the numbers are a production thing and doesn't mean a thing. I don't know.
As far as I can tell the numbers mean nothing to the user. However as has been said many shavers use them as an easy way to keep track when flipping the blade. I don't blade flip so they never had any significance for me. I don't pay any attention to which side of the blade is up when I put in a new blade, except for Russian blades with the wax spots on one side. These I always put in with the spots facing up towards the top cap.
The numbers are for the manufacturer. If a machine is causing a blade defect they can tell where the problem is on the production line by checking the number closest to the defect.
The numbers are actually one of the most important elements of the blade. The difference is pretty obvious when you look at the blade under a microscope. If you can't be bothered to notice the extra details when shaving, you're probably never going to get consistently good shaves. See the article for yourself Razor Blade Microscopy Analysis
Like the video above shows, they are immaterial. They are put there for quality control reference for the manufacturer. I had never even noticed them until a few months ago when this question came up on another board.
