Quote: "Sorxus"It's easy:
- Obverse: where is written ruler of country or country of origin.
- Reverse: other side.
As far as I'm aware, this works for most coins, but there are cases when coins don't fit neatly here; such as coins that express the country of origin on both sides, for example.
That being said I've always thought of the side with a monarch's portrait being the "back" of a coin. The reasoning of portrait/arms = obverse seems kind of arbitrary to me as well, but I have no problem with it.
It's not always the case, but the Obverse side is usually the heads side. It has either a portrait of the ruler of the country, or a representation of the country, like a coat of arms or a national emblem.