The date in the catalog of 1751 refers to the date publication started on the overall work, NOT THE DATE OF THE DATE OF PUBLICATION OF THE PARTICULAR PLATE. As can be seen below, the plate volume of the supplement WAS FIRST PUBLISHED IN 1777. I am sorry for any confusion caused by my inattention to details. I thought the plate copy was of very good quality and might be useful to some of our colleagues.
"The work comprised 28 volumes, with 71,818 articles and 3,129 illustrations. The first seventeen volumes were published between 1751 and 1765;" ... "11 volumes of illustrations, issued from 1762 to 1772." "En 1776-1777, Charles-Joseph Panckoucke et Jean-Baptiste-René Robinet font paraître un Supplément en 4 volumes de textes et 1 de planches."
Suite du recueil de planches sur les sciences, les arts libéraux et les arts méchaniques avec leur explication: deux cens quarante-quatre planches. (1777):
http://www.biodiversitylibrary.org/bibliography/82336#/summary
Denis Diderot (1713-1784).
http://catalogue.bnf.fr/servlet/autorite?ID=11931970&idNoeud=1.1.1&host=catalogue
Geneva edition (1779):
http://books.google.com/books?id=J4l_dZfGS9YC&pg=PA3
Of possible interest:
1762 edition- arts militaires plates:
http://www.elke-rehder.de/Antiquariat/arts-militaires.htm