Дробилка Serial No Rr marinosterlefotografo.eu. ruger single six serial # Ruger Forum. Oct 20, 2017 · fuzzybonz, You have a nice SingleSix there . first because it was sold as a OM Magnum model (no 22 LR cylinder) and secondly because the "D" in your S/N means it was a "duplie" serial number . in other words, Ruger screwed up and used the same s/n on two guns so the second one got a ...