

This is his official service or ledger number. This section was specifically established just before WWI to recruit experienced.
Civilian fishermen, deckhands, and engineers into naval service. The sailor's initial and last name likely. Indicating he was a merchant or civilian mariner mobilized. For military duty during wartime. Because your sailor has a "T" prefix.
He almost certainly served aboard a commercial fishing vessel that was requisitioned by the military. Clearing lethal minefields laid by German U-boats in British and Mediterranean waters. This medal is from an enormously large collection of worldwide medals. It is from an old well established collection of more than. 100 pieces which I will be listing over the next several months.
Please ask if you have any questions.