I often learn new things about our own collection from bookseller catalogs, and a colleague just sent me one about an important and rather chilling item. This is a 1551 decree from the Holy Roman Emperor requiring all Jews to wear a yellow ring in public (illustrated at the bottom right) nearly four centuries before the Nazi yellow star. The dealer said the Houghton copy was the only other one he had traced. https://id.lib.harvard.edu/alma/990041636810203941/catalog