Oil of Impact: This magical substance is charged with a powerful dweomer which has beneficial effects upon blunt weapons and missiles of all sorts, magical and non-magical. When applied to a blunt weapon such as a club, hammer, or mace, it causes the weapon to both be magical and deliver extra damage. When the oil is applied to a missile, its effect is to make it both magical and very deadly upon impact. Missiles upon which the oil of impact will properly function are hurled hammers, hurled clubs, sling stones, and sling bullets. A flask of this substance will contain from 3-5 applications. Each application will last for 9-12 rounds on a hand-held weapon, but when applied to a missile weapon the substance has but a single "charge." With respect to missiles, however, only a small amount need be used, so that 4-5 sling missiles or 2 larger weapons can be treated with a single application. If the oil is used on a hand-held weapon, its dweomer will bestow + 3 status to the weapon's hit probability and cause + 6 damage on a successful hit. Missiles will be + 3 both "to hit" and to damage.
I'm DMing a game and rolled this item up randomly. It seems like a monk could put this on their fists, gauntlets, feet, or boots, or any character with martial arts that inflict bludgeoning damage. But I'm not sure.
Seems like there's been a ruling on this before as a way for older edition monks to hit weapon resistant creatures. We have a monastic OA character who has a staff as well, so they can either wield the stick and make this work, or, if this makes sense, they can use the oil on their fists/palms. Their damage would be the same either way, so its more of an aesthetic ruling, but might be useful later for other purposes.