The Process - only one handwritten copy?

Security.


Also, there is no point in a back-up copy (other than the threat of fire) because once the book had been stolen, the value of the process is decimated. Some other company can now use it / sell the product, etc, even if you still have a copy.

Apparently his job is to invent things for the company. He's an inventor. Inventors use inventors notebooks:

https://en.wikipedia.org/wiki/Inventor%27s_notebook

They write down their ideas, and even now some of them indeed write them down in bound books. The bound part, and keeping the notebook somewhat secure, helps prove that you personally made it.

Not copying it? Security, as well as the fact it is probably not production-ready yet, but just an idea. Next they will get some patent attorneys, get some engineers in a room, etc.

Also: I assume an exaggeration. Our hero did it, so can reproduce it from his mind. The secret chalkboard is probably this same thing, since it's what's occupying all their time. But, it's hard to steal a chalkboard. They mean there is one easily portable copy of the complete idea.