Analysis of information sources in references of the Wikipedia article "Classical guitar" in English language version.
...According to the current historical records, Gaetano Vinaccia and his brother Gennaro were responsible for the creation of the first six string guitar sometimes around 1776 in Naples...Authenticity of his surviving guitar was often placed in question by modern historians...
A rather small sized vaulted-back guitar in the engraving by Etienne Picart (c. 1680) after the painting by Leonello Spada Concert (c.1615), Musée du Louvre, Paris