You gentlemen beat me to the punch regarding the Atlantic Star. It seems like an unlikely award to an RE officer. I know it was given to army maritime gunners, and RAF aircrew, but it seems odd on this uniform.
One qualification for the Atlantic Star was "six months service [afloat?] west on Longtitude 20 East". That would take in Greenland, Iceland and a small sliver of the extreme west coast of Africa - Ghana, Nigeria, etc. Maybe even the Canaries - I didn't check.
So, two theories: 1) actually for shore service in one of those places, perhaps as a harbour master or on dock construction, etc. Don't know if the regs support that but stranger things are known OR 2) I believe the Army already had some of its own ships - they certainly did post=war - run by the RAOC, I believe. So infact you might have a ship's "Captain" who was a major, captain or lieutenant. Shades of Catch 22!
(For our European brethern, BTW, Catch 22 - about the US Army Air Corps in Italy - had a character who'd been promoted ceaselessly until his rank matched his name and was Major Major
I can only find one McKay. 74044 Andrew Melville McKay R.E., enlisted into the Supplementary Reserve of Officers from being an Officer Cadet Sheffield U.O.T.C., in 1938. Relinquished his Commision 29th January 1964, retaining the Honourary rank of Major.
Try the question to the Corps of Royal Engineers Museum, at Chatham. As it is a little unusual they may answer.
Btw, we have here in Finland also Major as family name and there used to be one major Major ("majuri Majuri" in Finnish) who was used at tv news as specialist studio commentator when Gulf War started. He was promoted later on to Lt.Col Major!
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