This edition, published by Virtue & Yorston, New York, was edited by Charles Knight, who died while the edition was being prepared and who had edited earlier editions of Shakespeare's works. Knight (1791-1873) was an English publisher and editor.
His editions of Shakespeare were some of the most popular and widely distributed throughout the nineteenth century in England and the United States. There are many Knight editions of Shakespeare; the following is a brief version of a complicated publishing history.
The first one, Knight’s “Pictorial” edition, was published in parts from 1838 to 1841. In the introduction to the second revised edition of this edition in 1867, Knight wrote, "My own labours upon other editions, such as 'The Library,' 'The National,' and 'The Stratford,' had been devoted to the examination of new readings and recent views of the value of original copies. When, therefore, the publishers desired to confide to me the complete revision of 'the Pictorial Shakspere,' I did not come unprepared to the task." The “Popular,” the “Cabinet,” and the “Medium” editions were also based on Knight’s work.
Knight died at the age of 81 in 1873, the year the “Imperial” edition was launched. It was called "Imperial" because it was printed on large, imperial size paper. The “Imperial” edition was first published in parts with elaborate illustration plates by Virtue in London from 1873 to 1876. Virtue and Yorston came out with an “Imperial” New York edition in two volumes, dated variously 1873–76 and 1875–76. It is a nice edition to own but not particularly rare; at least 124 libraries are listed on WorldCat as having copies of the 1875–76 printing.
Besides many illustrated editions of standard works, including The Pictorial Shakspere, which had appeared in parts (1838–1841), Knight published a variety of illustrated works, such as Old England and The Land we Live in and – The Pictorial Gallery of Useful Arts, the latter based on the Great Exhibition of 1851. He also undertook the series known as Weekly Volumes, himself contributing the first volume, a biography of William Caxton. Many famous books, Harriet Martineau's Tales, Anna Brownell Jameson's Early Italian Painters and G. H. Lewes's Biographical History of Philosophy, appeared for the first time in this series.
In 1853 Knight became editor of The English Cyclopaedia, essentially a revision of The Penny Cyclopaedia. Knight also launched the Local Government Chronicle in 1855, and at about the same time he began his Popular History of England (8 vols., 1856–1862).
http://en.wikipedia.org/wiki/Charles_Knight_%28publisher%29
http://www.shakespeareinamericanlife.org/identity/bard/treasure/fieldguide6.cfm
Imperial ed., edited by Charles Knight