Kibble Balance as Operational Identity: Why ℏ is an Exchange Rate

We formulate a metrology-grade, non-circular operational identity for Planck’s constant,in the same spirit as our G-identity and TF/BTFR memory program. The Kibble balanceserves as a power ledger equating gravitational mechanical power to quantum electricalpower (Josephson+quantum Hall), thereby enforcing a unique universal coupling ℏ∗ thatlinks (i) phase and action, (ii) energy and frequency, and (iii) momentum and wavevector.The rectangle-loop lemma proves single-coupling consistency across these three interfaces.In the post-2019 SI, where h and e are fixed, the balance realizes the kilogram by tyinggravity to frequency standards. By uniqueness of the observable law and calibration protocol,ℏ∗ ≡ ℏ. We add an explicit derivation of the Kibble identity, an uncertainty-budget schematic(with units), and an empirical cross-check section (XRCD/Kibble/CODATA). No numericalprediction of ℏ is claimed.Keywords: Kibble balance, Planck constant, operational identity, Josephson effect, quantum Halleffect, SI 2019, metrology