Did I eat Field Ration D in the early 1970s?

I spent about the first three years of the 1970s in Cyprus - my father was stationed out there with the RAF. We were evacuated back to England hurriedly in the middle of the night during the Turkish invasion in 1974 - I was about seven years old.

Anyway, I have a distinct memory of (while we lived out there) being given a piece of ‘survival chocolate’ to taste.
The piece I was given was an enormous thick cube about an inch on a side that had been broken off a bar that came out of a grey cardboard box with plain text labelling or printing.
The chocolate was hard and crumbly - like overcooked fudge, dark in colour and tasting like burnt, sugary, gritty chocolate.

From time to time, this memory would surface in my mind (usually when I tasted something reminiscent of the stuff), but I only recently thought to google ‘survival chocolate’ and try to identify it.

My memory bears a striking resemblance to Ration D - the presentation and packaging of the bar match my memory and looking at the ingredients list, the taste and texture sound like they ought to be a reasonable fit too.

BUT… Production of Ration D ceased at the end of WWII - some thirty years prior to my consumption of ‘survival chocolate’.

So what did I eat? A thirty-year-old surplus item? Or was there some other similar product still in production/use by the British forces?

(for the record, I also came across ‘tropical chocolate’ in my researches, but the descriptions do not seem to match the thing I’m remembering)

In the 1980s, wildland fire fighters in the US regularly ate C-Rats and K-Rats, dating from WWII. Today we have gourmet meals, even on the fireline. It’s needed with a 6,000 calorie a day diet.