I learned about notch codes the hard way. I had just started working at a commercial lab and I was loading about 50 sheets of E-6 in a roller transport processor, you'd load 2 sheets at a time with the notches facing a certain way.
Halfway thru I thought one felt funny but just kept loading. As soon as I finished someone from the front desk came running back to see if I was done. I found out that the
one that felt funny was a sheet of Plus-X that got mixed in. Plus-X doesn't do to well in E-6 chemistry. Half the sheets of E-6 where ruined and I spent the rest of the day
dumping the chemistry and replacing it. I memorized all the notches after that.
i have been cross processed a few sheets of e6 and c41 by mistake in
b/w chemistry, not quite as bad as a roller transport machine
after 22 years, i still can't remember which way to load it in holders, notch on the top right or left
I thought for a second that the notch codes for Kodak Ortho-X corresponded to the sheets that I have, alas I had just misread the table. I have some Ortho-X film that has just a single rectangular notch, not the three notches that are usually listed. I think it must be from an early 1938 batch before they decided on what the notch code should be. The film develops best in paper developer with surprisingly little fog, given how old it is.