This essay examines a unique set of impressions of William Blake’s Illustrations of the Book of Job in the Beinecke Library, Yale University. The body of evidence it presents means that our understanding of the stages of production of this series of engravings now needs to be reconsidered. The Beinecke set, hereafter known as the Rosenbloom set, reveals the meticulous detail in which an artist and craftsman worked. The essay offers previously unrecorded information about the early stage of Blake’s engraving of the Job illustrations that will augment our knowledge of his working methods. It aims to record the details of the Rosenbloom proofs and revise the current sequence of pre-publication proofs set up by Robert N. Essick. It will be necessary to summarize Essick’s important work in order to give the full context for the development of the Job plates.