Andrea del Sarto (17c ?)

Still on the auction trail, I've been browsing Sotheby's online catalogue of Old Master Paintings, which come up for grabs in London starting 1 November. (The exhibition opens at Sotheby's New Bond Street showrooms on 26 October.) The catalogue is full of those weasel words "Follower of...", "Circle of...", "School of...", "After...", "Studio of...", Attributed to...", all of which means nobody has a clue who painted it! Then I spotted an Andrea del Sarto painting of St John the Baptist in the Wilderness with an estimated price tag of £3,000 to £4000! This is peanuts for a master of the High Renaissance whose works were considered perfection in their day! Wow! Star Buy of the Year! Coxsoft Art might raid its piggy bank for this one. Now the bad news. Sotheby's has dated the work as 17th Century. Whoops! Andrea del Sarto died in 1531. So, we have a mystery. On the left is a genuine Andrea del Sarto St John the Baptist (1528) in the Galleria Palatina, Florence. On the right is the mystery St John (17c.). Any offers?