WW1 Naval Officer Hat

Seems to me as the regular navy officers cap WWII. Flag rank.
Couldn't look if it could be WWI as i don't have documentation on the navy that era (or other era's).

For all WWII involved countries navy uniforms and ranks. Or many other WWII uniforms and gear (regular up to SS), including 'unknown' special german brigades (desert, jungle and such). Used arms by all countries (pistols up to planes). And some WWI doc.
One can always ask me as higly WWII interested and a lot of documentation.

 

I don't think MC stands for Marine Corps. When you see a Naval Officer referenced like this:
John Doe CDR, MC, USN
the MC stands for Medical Corps
Here's an example https://www.usni.org/magazines/proceedings/1955/april/navys-medical-problem

 

?? If i search for 'wwii US Navy Medical officers cap' i only a white version. Bmyut not the same as a summer cap (image above right) but with more decoration on the visor?
http://www.uniforms-4u.com/p-us-public-health-service-admiral-white-hat-18376.aspx
The medical seems to be the same as the standard flag rank hat, but then in white.

Sure this dark one can be from a medical officer?

 

This photo supports it.