This is an example of the slight variations that make this model collectible. Essentially same rifle, with knob on bolt handle flattened. Only produced in this configuration until 1972. Watch for fakes and read specialized material. Calibers such as 6.5 Rem. Magnum, .284 and .350 Rem. Magnum will bring a premium especially in RS model. Non-prefixed rifles exist in calibers and configurations other than those advertised by Ruger These should be individually appraised. Note: Add $400 for 6.5. Rem., .284, .350 Rem. Discontinued.