Complex sentence: It was owned by the New York art collector Jacob Reder from 1943 to 1969, and following Reder's death was bought by the art dealer Spencer A. Samuels, who believed it to be a Vermeer.
Split into simpler sentences: It was owned by the New York art collector Jacob Reder from 1943 to 1969. Following Reder's death it was bought by the art dealer Spencer A. Samuels, who believed it to be a Vermeer.