For serious collectors, condition is everything. A mint-condition Flash #123 can be valued at approximately , while later Silver Age issues in mid-grade (like #128) might range from £18 to £250 depending on their rarity and grading.
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For vintage issues, sites like Quality Comix and Judecca Comic Collectors provide graded copies and price guides for Silver Age classics like Flash #128 or Flash #143 . For serious collectors, condition is everything
High-value collector items starting with Flash Comics #1 (1940). For serious collectors