Upright the Knight of Coins is read as reliability, routine and hard work carried through without drama; reversed, as stagnation, an inflexibility that has stopped serving anyone, or work so cautious it never actually advances.
Court cards carry a double reading that the numbered pips do not: as a person, and as an influence or approaching quality rather than a person at all. As a person, the Knight of Coins is conventionally read as dependable to a fault, a colleague or partner who finishes what he starts but rarely surprises anyone; as an influence, the same card describes a period defined by patient, unglamorous progress rather than by any single event.
This is also the court card most often cited in discussions of the suit's reputation generally, since earth-suit court cards as a group are read, across all four ranks, as the most literally practical of the sixteen, concerned with money, work and material competence rather than ideas, feeling or action for its own sake. Where the Knight of Wands is read as impulsive and the Knight of Swords as reckless, the Knight of Coins is their opposite case, and readers commonly use him specifically to signal that a matter will be resolved by steady application rather than by a decisive stroke.
His reversed reading is correspondingly a caution against mistaking caution itself for progress, plodding work that has quietly stalled while still looking, from a distance, like diligence.