Reachability of eight certificate and accreditation registries, direct versus proxied

Whether the registries a buyer would use to check a supplier's certificates actually answer, measured on 2026-08-09 across ten hosts, three rounds each, from two egresses: a direct mainland-China consumer connection and a proxied one. Two controls ran in the same session. Results split three ways. Reachable from both egresses: IAF CertSearch (management-system certificates such as ISO 9001), the EU notified-bodies database, ILAC, and CNAS. Refused from both: UL Product iQ (403) and ISO's own standard listings (403). Reachable directly but not through the proxy: the FCC equipment-authorization entry and NHTSA vPIC. The controls behaved oppositely to each other — Baidu answered from both, Wikipedia only through the proxy — which is what makes the per-host differences readable rather than an artefact of one broken link. The practical consequence for a buyer outside China: which certificate you can independently verify depends on which registry holds it, and the answer differs by network path. This dataset does not explain why a given host refuses; it records what was returned. Method, per-host rounds and full write-up: https://currawongweb.com/verify/certificate-registry-access-study/