Observable state
Condition belongs to the object
Condition is the collectible's present physical state. It includes wear, marks, fading, staining, tears, losses, distortion, corrosion, brittleness, repairs, restoration, completeness, manufacturing quality and evidence of handling, storage or use.
Condition should be described before it is compressed into a label. 'Light edge wear, one shallow lower-corner crease, clean internal pages and moderate spine fading' preserves far more evidence than 'Very Good'.
Interpretive classification
Grade belongs to a system
A grade places the observed condition within a formal or customary hierarchy. That hierarchy may be numerical, adjectival, letter-based, component-based or qualified by terms such as restored, details, complete, unopened or factory sealed.
The grade is not embedded in the object. It is a conclusion reached under a particular standard, by a particular assessor, at a particular time. Two legitimate systems can classify the same physical evidence differently.
Contextual consequence
Value belongs to a market, purpose and moment
Value is an economic or personal conclusion. Grade may influence it, but so do rarity, demand, authenticity, provenance, completeness, originality, eye appeal, certification confidence, selling venue, timing and the type of value being considered.
A grade can remain unchanged while market value rises or falls. Conversely, an object can retain important historical, documentary or personal value even when its technical grade is low.