Ruger-57 pistols within this serial number range (641-00000 to 642-26274)
https://ruger.com/dataProcess/ruger57retrofit/
Ruger has discovered that a small number of Ruger-57 pistols may have right safety levers that do not meet our specifications and may be prone to cracking. Although only a very small number of pistols appear to be affected, Ruger is committed to safety and is asking owners of Ruger-57 pistols to perform a routine function check of the safety lever to ensure its proper operation and, if necessary, sign up for this retrofit.
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https://ruger-public.s3.amazonaws.com/safety/Ruger-57SafetyBulletin-3b792f8a6042.pdf
https://ruger.com/dataProcess/ruger57retrofit/
Ruger has discovered that a small number of Ruger-57 pistols may have right safety levers that do not meet our specifications and may be prone to cracking. Although only a very small number of pistols appear to be affected, Ruger is committed to safety and is asking owners of Ruger-57 pistols to perform a routine function check of the safety lever to ensure its proper operation and, if necessary, sign up for this retrofit.
&
https://ruger-public.s3.amazonaws.com/safety/Ruger-57SafetyBulletin-3b792f8a6042.pdf