We construct a canonical centered heat trace and its Mellin/zeta regularization for the GL (1) operator from HP--II. This yields a canonical zeta determinant \ _^can (L+) \ and a scheme-independence theorem reducing any admissible cutoff/subtraction scheme (, , P₅₈₍₀₋) to the canonical object via an explicit entire correction factor. We also prove the canonical normalization limits needed to remove the constant ambiguity in the quotient \ Q (s) \;=\;D₂₎₌ (ₒ) (s) \,. \
Tosho Lazarov Karadzhov (Tue,) studied this question.