Catalog of all countries and series with freshness metadata (free)

Filter to series at the given verification confidence (comma-separated). primary = no verification limitation recorded — the absence of a known problem, not a fresh re-verification. secondary = corroborated but the primary instrument was not read, usually because the publishing host blocks automated access. attested = no primary source is publicly available to anyone. derived = computed from another series. Unknown levels return 400 with the valid set.