Mark: [This is] a Russian-built GST, complete with an indigineo US bow turret. The plane was photographed in 1941 from a B-18 assigned to escort it and another GST to Sand Point NAS near Seattle. The two flying boats were carrying a delegation tasked with working out the details of the US-to-Russia lend-lease program.
Eric: Correct me if I'm wrong, y'all, in classifying this as a PBY-1.
(Photo courtesy of Mark Aldrich / San Diego Aerospace Museum)