Michelangelo's sculpture of the Pieta (1498-99), in the Basilica di San Pietro, is not only one of his most exquisite creations, it is also the only work of art he ever signed. Giorgio Vasari (1511-74) explains why he did so in his book The Lives of the Most Excellent Painters, Sculptors, and Architects (first published in 1550, enlarged in 1568):
“One day coming into the place where the Pieta had been installed, Michelangelo found a large number of strangers from Lombardy praising it highly. One of them asked another who had made it, and he replied: ‘Our Gobbo from Milan’. Michelangelo kept his counsel though it seemed rather strange to him that his painstaking work should be attributed to someone else. One night, bringing his chisels along, he locked himself in with a little light and carved his name there.”
The gobbo (hunchback) in question was Cristofero Solari (c.1460-1527), a sculptor from Milan, who had achieved fame in Rome working for Pope Alexander VI (r. 1492-1503).
The inscription in Latin can be seen on the Virgin’s sash and reads, in translation: 'Michelangelo Buonarroti, Florentine, was making (this)'. The word faciebat (was making) lacks the final letter, an omission that has been seen as a subtle play on the meaning of the word itself.
According to the ancient Roman writer, Gaius Plinius Secundus (23-79 CE), better known as Pliny the Elder, it had been the practise of some sculptors to inscribe the past continuous (faciebat/was making) rather the simple past (fecit/made), to imply that the artist had broken off, unable to bring his work to the perfection of the image he had in his mind.