Notes on verification

Core claim (Burgess leaving a leather briefcase behind when fleeing to Moscow in 1951) is corroborated by multiple independent sources tied to MI5's 2025 National Archives exhibition. The specific 'battered' descriptor is not explicitly confirmed in sources, and one source notes there were actually two briefcases involved, adding nuance not captured in the original claim. [tier=unverified indep_score=0.3 clusters=3 claim_tier=notable] [rescored 2026-09-15: curated origin-host map (PR #65); unclassified hosts no longer scored as aggregators]