I believe it is Kingdom of Canada, Kingdom of Australia and united KINGDOM
They are the "old style" IYRU 2-letter national ids.
Most of the old UK colonies ids' started with "K".
For example: KB (Bermuda), KZ (New Zealand), KH (Hong Kong), KR (Rhodesia), KK (Kenya), etc.
I thought it was curious that the proposal (from Europe) didn't include the option to use the current 3-letter ISAF ids, but I think the idea was to reduce workload on the scorers, so it made some sense to stick with the current ids.
Cheers,
Geoff S.