It was first published in 1968, reprinted in 72, 73, 75 and 78, by Oxford Univ Press (very reputable aren't they?).

My copy also has a note on the text, indicating that it "is taken from the 'third edition corrected' (1776), as presented by Sheridan to Garrick and now in the Dyce Collection of the Library of the Victoria and Albert Museum." The editor also notes that he has modernized the spelling such as changing -'d endings to -ed, modernized some of the 18th century spellings (like sofa for sopha, stupefy for stupify, chooses for chuses etc. No comment on the the z---ds and d---d though.