A little over a year ago, the New York City art dealer Robert Rogal received a visit to his private showroom from a young woman, who seemed eager to offload a family heirloom. Introducing herself as Karolina Bankowska, she carried a framed painting signed by Andrew Wyeth, resembling the watercolor landscapes the celebrated artist had completed early in his career. Intrigued, Rogal accepted the piece on consignment, figuring it might fetch between $20,000 to $30,000 at auction. “The provenance was a little fuzzy,” he said. “But she seemed credible. It wasn’t an obvious counterfeit.” NYC art dealer Robert Rogal, pictured with his late wife Gail, was fooled into accepting a purportedly fake Andrew Wyeth painting by father-daughter duo Erwin Bankowski and Karolina Bankowska.…