It is easy to pseudo-identify a magic candle. When lit, it has light radius 3 versus 2 for wax candles and tallow candles, and unlike ordinary candles, will not appear as partly used. Magic candles also cost much more than ordinary candles (250?) but cannot be sold, even at the lighting shop (Izchak will "seem uninterested").
Magic candles are particularly useful for Polearm and Lance users (Yeomen and Knights), and those who prefer to use Jumping Boots. You cannot Pound or Jump to spaces you cannot see. Magic candles are prefereable to Magic lamps as permanent light sources because they are lighter and wishable, and the light radius is identical.
The Candle of Eternal Flame is the quest artifact for Flame Mages, conferring warning, teleport control, and cold resistance when carried. When invoked, it summons a tame fire elemental. It is lawful for wishing purposes.