Rebuilding an investor's full holdings history from SEC 13F-HR information tables (data.sec.gov submissions JSON -> filing folder index.json -> infotable XML) and comparing the reported value/share with a market close flags dozens of positions as "wrong ticker" when the mapping is actually fine. Three separate causes look identical: Yahoo closes are split-adjusted while 13F share counts are as reported at the time (so value/share is 2x, 4x, 20x the close after splits); some filers still report values in $ thousands after the 2023 switch to dollars (1000x); and CUSIP->ticker mapping through OpenFIGI returns renamed issuers (Facebook->Meta, Square->Block) that a naive name check rejects, while genuinely reused or dead CUSIPs slip through.

You want to find companies currently valued below what large strategic corporate investors paid for their stakes. Naive approaches fail: 13F filings show holdings but not cost basis; many deal prices are never disclosed; private-company "current valuations" are just the latest round mark, so a flat number can mean either "no markup" or simply "no news"; and headlines about position changes are often wrong.