Sets where the head of state appeared on some but not all obverses

[<k>]

My home country of the UK (and its predecessors) has long featured the monarch on the obverse of every coin.

However, that is not always the case in countries. Above you see the current Spanish euro set.

[<k>]

When Tonga's new design series of 1975 was introduced, the King now did not appear on all the coins.

[<k>]

Denmark is another example.

[<k>]

Same for Norway.

[<k>]

The monarch appeared on the obverse of all the predecimal Fiji coins - EXCEPT, for obvious reasons, on those low denomination coins that were holed.

[<k>]

The coinage was used for British West Africa, which was a currency union.

It also included holed coins below the value of threepence.

Therefore the monarch did not appear on every obverse.

[<k>]

The same was true for the currency union of (British) East Africa.

[<k>]

In Southern Rhodesia also, the coins below the threepence did not show the monarch's portrait.

[<k>]

The same was true of Rhodesia and Nyasaland.

[<k>]

In Greece under the monarchy, only the coins of 50 lepta and above carried the King's portrait.

I wonder where and why this sort of split originated?

[<k>]

By contrast, in Sweden it appears that the highest denomination does not portray the king.

[Alan71]

in my home country of Britain (and its predecessors)

Apologies for being pedantic but I'm not sure "Britain" is a country in the current terminology.  The country you refer to is England, and the state being the United Kingdom of Great Britain and Northern Ireland, with "Great Britain" in this case referring to the geographical island containing the bulk of England, Scotland and Wales, all of which these days refer to themselves as countries...

[<k>]

I'm well aware of all the anomalies, but I was writing loosely and colloquially rather than academically.

Wikipedia:

Sometimes countries refers both to sovereign states and to other political entities, while other times it refers only to states. For example, the CIA World Factbook uses the word in its "Country name" field to refer to "a wide variety of dependencies, areas of special sovereignty, uninhabited islands, and other entities in addition to the traditional countries or independent states".

The Standard Catalog (sic) of World Coins requires me to look under "Great Britain". Even the term "the United Kingdom of Great Britain and Northern Ireland" could be mistakenly understood as "the kingdom of Great Britain" and "the kingdom of Northern Ireland" united together.

Anyway, if my home country is NOT Britain, how come my citizenship is British and not "United Kingdomish"?

[<k>]

Belgium under Nazi occupation. The denominations below 5 francs did not show the King's portrait.

[FosseWay]

By contrast, in Sweden it appears that the highest denomination does not portray the king.

None of the series of Swedish coins since the modern currency was established in 1874 have shown the royal portrait on all coins. Those that don't generally have the royal monogram, three shields or other state symbol.