Among the some 1,500 artworks found in Cornelius Gurlitt's hoard, 14 were proven to have been looted under the Nazis. The last of these has now been sold at auction.A pencil drawing by Carl Spitzweg auctioned at Christie's on Wednesday would not normally have garnered much attention. After all, the small-format portrait didn't break any auction records — even though it reached a far higher price than the auction house's initial estimate of €1,000-1,500 ($1,300-1,700), ultimately fetching €18,750. It's the drawing's provenance that makes it so provocative: The work was originally owned by Dr. Henri Hinrichsen, a Jewish music publisher...