My dad has found a photo of my great, great uncle and my great, great auntie at their wedding. We think the photo is circa 1925. We believe he was in the British merchant navy or marines, but we're not sure.
Hopefully his uniform gives some clues as to his rank or shipping line for some eagle-eyed Redditor!
Photo: https://imgur.com/a/XBCyxsm
Hello there! As your question is related to looking for identification/information regarding military personnel, our Guide on Military Identification may be of use to you. It provides a number of different resources, including how to request service records from a number of national agencies around the world, as well as graphical aids to assist in deciphering rank, unit, and other forms of badges or insignia. While the users here may still be able to lend you more assistance, hopefully this will provide a good place to start!
The cap badge looks like Merchant Navy officer's:
And I think the cuff insignia is that of a 2nd Officer, which would also be the same (albeit with different colouring) for the Purser, 3rd Engineer, Doctor and Dentist. The image isn't hugely clear though, and i'm not totally happy calling it. Do you have any other information about the chap?
Up to some point during the early 20th Century, the service was also known as the Mercantile Marine, which may help with your research.