I know this an old thread but what the hey.
The cap style looks different to most RN caps, even the older examples. The chinstrap is incorrect as are the side buttons, so as Odulf suggested I would say the cap was made for a MN Officer, perhaps around the 1920s.
Is the sweatband quite narrow? and how deep is the peak?
The cap badge and band are hard to date but are probably 1953 to late 1960s.
Oli