To prove that a fake is a genuine masterpiece is glory. Tall, lanky, bespectacled Kurt Sundstrom, a young man of gravity and wit, the associate curator of the Currier Museum of Art in Manchester, N.H.

Four of Basquiat’s paintings have been on display at the Currier since the fall, alongside Ouattara Watts, a renowned African and Western aesthetic painter. The exhibit is coming to a close this ...