If the caption is correct this is the Seagull ( the personnel are certainly Japanese Navy); no serial is visible but may have been removed from the wings after delivery as the Navy put their designators on tail or mid-fuselage.
It seems to be a magazine article. I've also included (more for my future reference) an interesting contemporary series on these boats.
The Seagull for Japan is thought to be a Mk.II (Napier Lion) but their serials were N9562--9566. But several were convertions or modifications so as you say confusing.
Regards
Nick
http://aviadejavu.ru/Images6/FT/FT1922/11/655-1.jpg
https://www.aviationancestry.co.uk/?...=ASC&pageNum=3