Hello Stig,
While I certainly am not able to rule out the aircraft as a PH-3, are you certain that all PH-2 were withdrawn by 1941. Looking at
http://niehorster.org/013_usa/_41_uscg/_uscg.html PH-2 appear to still have been in service, albeit I see from their locations that the photo is statistically far more likely to show an Atlantic, rather than a Pacific based machine.Also see
https://bluejacket.com/ww2_12-07-41_uscg_aircraft.htm I think given the author we can take it as given that the PH-2 remained in service.
Regards,
Clint