Looks like a Marlin 336 SC-Sporting Carbine. The R prefix indicates 1957/1958 date of mfr...could be either year, but leans to 58. The sporting carbine is a premium model and is a really nice rifle. Value is going to depend on condition, which is hard to tell in detail from the pictures, but overall it looks good from here. Look for undamaged screw heads, clean bluing without worn spots, pitting or rust on the barrel or receiver and in the bore. It would be valued at a premium over the standard model regular carbine and is sought after by Marlin fans. .35 is a great caliber in my opinion and also adds value, although could be an issue in these days of low ammo inventories. It is a hard hitting round that seems to outperform the expectations of the ballistics numbers in the field. Very nice rifle. Take good care of it.