A manuscript described as a fair copy may look orderly and carefully prepared. That description concerns its apparent finish; it does not by itself settle every question about the authority of its text.
Read the term in its catalogue context
The Folger glossary of manuscript terms contrasts a fair copy showing polish with drafts or foul papers. The glossary’s historical context should remain visible when applying the vocabulary to a particular collection.
Write down who uses the term and which features they identify. A neat hand and few corrections may support a description of presentation, while questions of authorship and textual history require other evidence.
Avoid building a hierarchy from appearance alone
A rough draft may preserve a significant revision that a clean copy conceals. Conversely, a clean copy may provide a more continuous reading. Their usefulness depends on the question you are asking.
When comparing witnesses to a historical work, keep material description, dating and editorial judgement in separate lines of your notes. That organisation prevents an attractive page from acquiring authority simply through its neatness. The label becomes a precise observation to investigate, rather than a shortcut to deciding which version must be closest to an original.