We must now go back to the year 1452, which is generally fixed upon as the date of the invention of engraving on metal (Fig. 262).[41] When discussing the subject of “Goldsmith’s Work,” we mentioned, among the pupils of the illustrious Ghiberti, Maso Finiguerra, and stated that this artist had engraved on silver a “Pax” intended for the treasury of the Church of St. John. Certain writers having recognised in a print now in the Imperial Library of Paris, and also in another print in the Library of the Arsenal, an exact impression of this engraving, were led to attribute to the celebrated Florentine goldsmith the honour of an invention in which he might perhaps have had no share at all. Possibly this process of printing off an impression, which was a very natural thing to do, had been actually practised by goldsmiths long before Finiguerra; they wished, doubtless, to preserve a pattern of their _niello-work_, or to see how it progressed in its various stages. The proofs, thus taken off by hand, having been lost, Finiguerra may have been considered the originator of a method which he only applied as a matter of course to his goldsmith’s work. The two circumstances--that the plate is made of silver and not of any common metal, and that it may be classed among the numerous _nielli_, engraved plates of decorative goldsmith’s work, which have been handed down to us and are of even earlier dates--will alone suffice, in our opinion, to dispose of the [Illustration: Fig. 262.--The Prophet Isaiah, holding in his hand the saw which was the instrument of his martyrdom. (Fac-simile from an Engraving on Copper by an unknown Italian Master of the Fifteenth Century.)] idea that this work was expressly executed in order to furnish impressions on paper. It was nothing but chance that in this case introduced the name of Finiguerra, which would not have become known in this connection, if it had not been for the preservation of two ancient impressions of his _niello-work_; while those taken from other and perhaps older plates had been destroyed. Thus the date, or the asserted date, of the invention of engraving on metal was fixed by the ascertained date of the piece of goldsmith’s work.