George Brett 2023 Donruss Mr 3000 #12 #190/349

George Brett Price List - Supercollector Catalog

PSA Magazine: 2022 August #008 by PSA Magazine - Issuu

2023 Donruss Baseball - Trading Card Database

Sold at Auction: (NM/MT) 1979 Topps George Brett #330 Baseball Card - Kansas City Royals- HOF

George Brett Price List - Supercollector Catalog

2023 Donruss Baseball Mr.3000 #12 George Brett /999 - Kansas City Royals

Calaméo - 2023 Summer Auction

SABR's Baseball Cards Research Committee – Page 27

2023 Donruss Baseball - Trading Card Database

Cardboard appreciation: 1981 Topps Traded Darrell Porter

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