These are the spine lables on several volumes of Leupold's Theatrum Machinarum - just as they are shelved in the Iron Library. They caught my eye even though they hide in a corner of the room where our rare books are shelved - as if they wanted to show that the Theatrum Machinarum is not a book like any other.
If you visit the Iron Library, you will have the opportunity to examine all volumes of Leupold's great work in the original. The Iron Library owns all the volumes, some of them even in several editions. Two volumes have just been "retouched" by the book restorer, who has dressed their covers in fresh kiebitz paper.
The best and quickest way to get an impression of the contents of the Theatrum Machinarum is to look at the copperplate engravings they contain.