The general belief is that the three regard the Holy Trinity and not an uncommon decoration on Axes and other arms/armour. I have my own pet theories on some common fetishes such as hearts. If we look at the tarot, one finds the suits representing the merchants/taxes (pentacles/diamonds), royalty and religion (hearts), common man (wands/clubs) and the military (spades/swords). Clubs representing common man, the executioner's sword and the decoration might well represent the justice of the common man.
FWIW
GC