a patent, invention, model or design (whether or not patented), a secret formula or process, a copyright, a literary, musical, or artistic composition, a letter or memorandum, or similar property, held by—
(A)#
a taxpayer whose personal efforts created such property,
(B)#
in the case of a letter, memorandum, or similar property, a taxpayer for whom such property was prepared or produced, or
(C)#
a taxpayer in whose hands the basis of such property is determined, for purposes of determining gain from a sale or exchange, in whole or part by reference to the basis of such property in the hands of a taxpayer described in subparagraph (A) or (B);