ok. sorry, didn't realise there were 2 definitions.
I went by US definition, Gef has British definition.
Quite why they're different I don't know, but then lots of measures have the same name, but different quantities between Imperial and American.
I would still say 100� proof Southern Comfort would be 50%ABV because it's an American spirit. Bacardi 155 is viscious stuff - 155� proof, 75.5% ABV, that's from over America way, though why the Cubans use the American system I don't know.