A quick skim through the BBC!Ghosts tag tells me that no one has spent too much time trying to decode the Captain’s service ribbons. Lucky you, I did!

The badge on his jacket lapels say that he was in the royal artillery

1939 to 1945 Star: This is awarded to anyone who completed operational service overseas between 3 September 1939 and 8 May 1945 for at least 180 days.

France and Germany Star: Awarded for at least 1 day of operational service in France, Belgium, Luxembourg, The Netherlands or Germany between 6 June 1944 and 8 May 1945.

Defence Medal: Awarded for non-operational service (like training bases, for example) in the UK or overseas. A minimum of 3 years service in either the UK (3 Sep 1939 and 8 May 1945) or in the Home Guard (14 May 1940 and 31 Dec 1944) are required; if stationed overseas, 1 year between 3 Sep 1939 and 2 Sep 1945.

War Medal 1939 to 1945: Awarded to all full time personnel of the armed forces who served at least 28 days between 3 September 1939 and 2 September 1945, no matter where. In Europe, WWII ended in May 1945; this medal was instituted in August 1945.

He doesn’t wear any other clasp, so he didn’t fight in the Battle for Britain or the Battle of the Atlantic (makes sense, those were RAF and Navy stuff mostly). The Africa Star was awarded for a minimum of one day of operational service in North Africa, the Arctic Star was awarded for any amount of time spent fighting in that campaign, and the Pacific, Burma, and Italy Stars were awarded upon entry into an operational area. He was awarded none of these medals, which means he only fought the France and Germany campaign.

He only wears WWII medals, which means he didn’t fight in WWI (it was unlikely he would have anyway, tbh, 41 was the the maximum age to fight in WWII, which would have made him 18 in 1916). The order I’ve written them out in (from top to bottom) is the order they should go left to right. For some reason, the Captain is wearing the ribbon band upside down. That’s a very huge big no good no-no. At first I assumed if was a mistake by the costume people, but it’s been three seasons and that hasn’t been fixed yet so I have to conclude it’s intentional. It could be some kind of BBC directive (idk, “non-army personnel has to wear the uniform in a certain way or it’s an insult to the queen” or some other silly nonsense) or it could be a genuine mistake the Captain made before dying, in which case I assume he’s spent sixty years being massively bothered by this. [ @lagoonnebula6523 said that the director of series 1 and 2 hinted that the reason for this mistake would be revealed in a future series, which I think points to an in universe explanation. Thank you for the info, this is super cool to know!] [Small aside, but I remember googling why the ribbons would be worn upside down and what i found was neat but probably unrelated. Check the tags if you’re interested]

I believe he’s in a service dress, which basically means he was at some kind of event when he died. He’s not in the army equivalent of the white tie, so we’re not talking about something too fancy. Maybe some sort of minor party?

So yeah, dude died after the war ended, and considering he seems used to saying “king” instead of “queen” I feel like he died either before Elizabeth was crowned or just after, so somewhere between August 1945 and around 1953-55