Reproducing a painting on a coin is a genuine technical problem: the original has scale and brushwork, the coin has forty millimetres and a press. Mints solve it with fine colour printing, selective gilding and relief that lifts the composition off the field.

Architectural subjects take the opposite approach, using deep relief to give a facade or a dome real dimensional depth. Both are themed issues, so the engraving rather than a licence is the whole appeal.