How can I tell when I make an offhand punch attack?

I am working on a Hill Orc Gladiator of Uskayaw that uses a combination of one-handed axe and offhand punches to maximise hits per turn thus maximising piety gains thus putting that sweet, sweet +3 Invocations aptitude to a real good use. At least, that's a working theory.

The problem is, I can't tell when my character is making an offhand punch attack. This is problematic, since without knowing that I can't really gauge the effectiveness of my strategy and can't decide when to stop pouring loads of XP into Unarmed Combat skill.

I know that an untrained character without armour has a 33% chance of making an offhand punch, and that this chance goes up with Unarmed Combat and down with encumbrance (whose effects are reduced by sufficiently high Armor skill). However, when my most successful run had 8.0 in UC, 6.6 in Armor and a plate armour, I still couldn't quite pick out anything from Ctrl+P log that looked like offhand punches.

So: how can I tell when I make an offhand punch attack?

(Just to rule out rookie mistakes: I am not using any shields: no buckler, no big shield, no great shield. And the weapon is my starting war axe that you get with Gladiator background, so yes, it is one-handed.)

(I'm playing 0.19, not the current Trunk.)