Here's a mystery picture from way back of eight young sailors with their petty officer in the middle of the front row.
Why the photo ended up in an old family Bible, tucked away in the pages of Matthew's Gospel which was left with collector of military memorabilia Gary Campbell by an anonymous caller, is part of the mystery.
"Unlike most Bibles of this nature, there were no names or addresses of the owners that I could make out," explained Gary, from Templepatrick.
"However, there was a tattered note pinned to the picture saying one of the seamen was from Northern Ireland.
"But there was no indication which sailor was being referred to. I reckon, from the state of the note and the ragged Bible, which dated back to the early-1930s, that the photo was slipped into the Holy Book a long time ago and forgotten about.
"I only discovered it when I was leafing through the pages and out popped the picture, which is baffling me. It had probably been in that Bible for years and years."
So I turned to two other experts in military and aviation history – Ernie Cromie of the Ulster Aviation Society and the historian Richard Doherty.
Between them, they reckon the photo was taken 90 years ago – in 1923 – not on a ship, but at a shore base in Chatham called HMS Pembroke.
It turns out that the original HMS Pembroke was a 28-gunner, launched in 1657 and sunk in a collision two years later.
Down the years there have been seven Royal Navy vessels called Pembroke right up to a modern minehunter launched in 1997 and still active.
And as well as the ships, there have also been Royal Navy shore establishments around the country called Pembroke for some curious reason, including the one where the picture was probably snapped at Chatham. One or two ships, such as HMS Duncan and HMS Achilles, were also renamed Pembroke and served as base ships at Chatham and elsewhere.
But which in the line-up of young seadogs in the picture is the Ulster connection?
Gary, Ernie and Richard would love to solve the mystery with our readers' help.
Gary said: "I'm convinced the photo belonged originally to the family of a young seaman from Northern Ireland and was forgotten and lost after being tucked away in the Bible for safety."
He's hoping the Pembroke picture puzzle will be solved by the time seafarers, aviation buffs and their friends gather at a show at the Maze on Saturday, August 24, organised by the Ulster Aviation Society to commemorate the 70th anniversary of the Second World War Battle of the Atlantic.