In this artwork, how is the Attribution discussed?
Ernest II of Saxe-Gotha-Altenburg acquired the Portrait of a Man in a Wide-Brimmed Hat for the Gotha ducal collection in 1804. There it was at first attributed to Thomas de Keyser, but Schneider (1854), Ernst Wilhelm Moes (1909), Cornelis Hofstede de Groot (1910),  Wilhelm von Bode (1914), Wilhelm Valentiner (1923), Frans Dony (1976), and the Herzogliches Museum all attribute the painting to Frans Hals. Some other authorities, such as Seymour Slive, do not. In his 1974 catalogue, Slive lists the portrait but glosses its attribution to Frans Hals as ("D" for) doubtful – he had not had occasion to inspect the original work. In accord with Slive, Claus Grimm's 1989 catalogue omits the portrait from the works attributed to Frans Hals.When the painting was recovered in 2019, the Herzogliches Museum had it examined for authenticity at the Rathgen Research Laboratory in Berlin, which conducted infra-red reflectographic, radiographic, and macro analyses. Based on the report from the Rathgen and on Kleinert's opinion, the Herzogliches Museum concluded that the portrait is indeed the work of Frans Hals himself.
Claus Grimm 1974 catalogue Gotha Rathgen Research Laboratory radiographic Ernest II of Saxe-Gotha-Altenburg 1989 catalogue Seymour Slive Thomas de Keyser Wilhelm von Bode Cornelis Hofstede de Groot Hofstede de Groot Ernst Wilhelm Moes Wilhelm Valentiner infra-red reflectographic Frans Hals