I went to the Gutenberg exhibit and learned that way back then, the most frequently-used letters, the small ones, were kept in the part of the case that was nearest to the
printing person, which was the lower part of the case. Sounds definitive to me.

Louisville is the only place in the States that is getting this exhibit (at least for now), because we are a sister city to Mainz.

I also learned that we indent paragraphs because they used to leave a blank space on the page, so that the first letter could be illumined (drawn large, and very colorful,
full of swirls, etc.).

They had actual books from the 1500's!!

And, the first Bible printed in America, in 1663,
was printed in Natlick, an Algonquin language! They had it there!