Visible (in 600dpi scans) are the letters "oast Guard" at the base of the tail. Below that are the letters "V-1", followed by two very blurry letters resembling "98". They are probably "89", which would make this V-189 (BuNo 2290) - the Coast Guard's first PBY.
William Scarborough confirms this plane as V-189 (BuNo 2290).
PBY Catalina In Action p23
( Photo from author's collection )