A naval captain sits for his portrait at the studio of W. V. Amey in Portsmouth, Great Britain. I am uncertain about his rank. Perhaps a visitor to this page can provide helpful information to determine his rank and country of origin. Portsmouth was a significant naval port for centuries, including at the time of this photograph. The photographer advertises that his studio was patronized by the late Majesty Queen Victoria which confirms that the photograph was taken after 1901; the year of her death. This portrait cabinet card is in good condition (see scans).
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THE CABINET CARD GALLERY 
I believe this is an RN petty officer, based on (1) cap badge, (2) six buttons on coat v. 8 for officers, (3) absence of cuff rings indicating rank, and (4) buttons on cuffs. Not sure why there’s no sleeve badge on the upper arm, but otherwise it’s correct for a petty officer.
Yes, this appears to be an RN petty officer, because of all the points Andy Hall cited. As he mentioned, it is peculiar that there’s no sleeve badge indicating his department of service (engineering, gunnery, torpedo, and so on).