Wow, an answer!:)

I looked up the N number on the registration page at Aerofiles.
NC398N was assigned to a Rhon Ranger glider, I have no idea what that is.

Well, that’s not so hard. One of these old, completely open gliders.
http://victoriancollections.net.au/items/50e3ab742162ef035405ffa0

NC399N is assigned to a Aeromarine B. ???? Attached is a photo

Yes, there are some more pictures of this one around. But there is no description of a “B” type – verification not possible! Anyway, it is a progress when aerofiles confirms the existence of a type “B”.

Thank you Aero Gator!

Regards, RT