Did Achim Leistner's hand-polishing ('atomic feeling') actually outperform machine methods on the Avogadro spheres, and is the account corroborated beyond the Powerhouse Museum caption?

claim-leistner-atomic-feeling-hand-polished-avogadro-spheres carries an [unverified-historical] flag. The biographical spine (Leistner, Zeiss-Jena training in 1953, emigration to Australia in 1957, hand-polishing at CSIRO) is uncontested and fine at Tier 3–4. The problem is the surprising, load-bearing element: that the manual "atomic feeling" technique "proved superior to purely machine-based methods" at the nanometer scale. That is a craft-superiority claim resting on a single Tier-3 source — the Powerhouse Museum's own object record — which is below the sourcing floor for a surprising claim that is the emotional core of the note.

Why it matters

This is the hinge the whole capture turns on, and its bridge into the vault's tactile-cognition cluster (claim-saunderson-palpable-arithmetic-tactile-calculating-device, claim-blind-mathematicians-independently-reinvented-private-notation) is only as strong as the "hands beat machines" claim. Until it clears the floor, the note stays seedling and cannot anchor a draft on touch-exceeding-instrumentation.

What would answer it

• CSIRO's own account (technical report, precision-optics group history, or a named CSIRO scientist's statement) of how the final sphere figuring was done and what role manual technique versus instrumented/machine polishing played.
• A metrology or optics-journal write-up (Tier 1–2 — e.g. Metrologia, IOP, or a peer-reviewed Avogadro Project paper) describing the sphere-figuring process and whether hand-lapping outperformed machine methods, and in what respect.
• Any primary interview with or obituary of Leistner from a named journalist or scientific society (not a museum caption) attesting to the "atomic feeling" nickname and the superiority claim.

Candidate next moves

Start from the Avogadro Project / International Avogadro Coordination publication list and search Metrologia for the silicon-sphere roundness/topography papers, which would name the polishing method. Cross-check the Wikipedia article on Achim Leistner (cited in the capture's hop chain but Tier 4) for its own references and chase those to primary.