There are three editions of the Encyclopédie in the Voltaire Room:
Taylorian I - the Panckouke edition
Taylorian II - the Readex facsimile edition produced by Pergamon Press
Taylorian III- the 'original' edition
The first volume of the original Taylorian edition has the date of publication as 1751 but was in fact printed for additional subscribers in 1754. The second volume has 1751 as the date of publication but was in fact published in 1754 and the third volume has 1753 as the date but was in fact published in 1754. Both also being printed for additional subscribers.
The facsimile edition uses a reproduction of the title page of the original first three volumes. The first vol has 1751 as the date of publication; vol 2 gives 1751 as did the original vol. 2 although published in 1752 and vol.3 is dated 1753.
The Panckoucke edition was in fact a reprint produced in 1770 but using the same dates of publication as the original edition (1751, 1751, 1753). The first three volumes of this edition were impounded and kept in the Bastille. Later on they were freed and a limited number of sets were made up from surplus vols. of the original edition 4-17.
The encyclopédie is also available online