[3crows]

I'm not too sure who makes them, both on these lever-actions came equipped with them.

Marlin used the sight systems from here (both JM and REM) for the SBL:

Marlin 336 Sights | Marlin 1894 Sights | Marlin 1895 Sights

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Ruger now makes their own similar but proprietary system for the SBL. The TSBL under both REM and Ruger get the Skinner sights.