Not so much a cursed item as it is a largely ineffectual one, this will appear as a case of Healing Potions for Cure Serious Wounds, with a total of six bottles. The bottles are extremely fragile, so the case is made of iron bound wood, and is heavy for its size (50 pounds). Anything less protective than this will surely result in the potions breaking; opening and transfering the contents to other containers will spoil them. Despite this inconvenience, these will seem to be the real thing to all magical tests.
When actually used to heal someone, each potion will only cure 1 HP of damage, no matter what. All that care, and lugging around the heavy case will have been for almost nothing.