Potentially affected pistols include any Ruger-57 pistol with a serial number of 642-26274 or lower (including all Ruger-57 pistols with a “641” prefix). If your Ruger-57 pistol is within this range (641-00000 to 642-26274), you should follow the inspection procedure outlined below to determine whether your pistol requires a retrofit. Ruger-57 pistols with a serial number of 642-26275 and above are not affected by this Safety Bulletin.
More information available at Ruger:
https://www.ruger.com/dataProcess/ruger57retrofit/?r=y
Printable Safety Bulletin:
https://ruger-public.s3.amazonaws.com/safety/Ruger-57SafetyBulletin-3b792f8a6042.pdf