The remington 600 was produced in 2 different versions.the 1st version was produced 1964 to 67 it had a plastic rib vent on the barrel cals included 222rem,6mm rem,243win,308win and 35rem.it had 18 1/2" barrel and monte carlo stock.the 2nd version the 600 mohawk was produced from 1971 and discontinued in 1978. it was also available in 222 rem,6mm rem,243win,308win they dropped the 35rem for this run .this rifle did not have the rib vent barrel but was still produced with the 18 1/2" barrel the stock is plain walnut with pressed checkering.the one I have here in 308 has a serial # 6647### and was produced in 1973.should also mension that at one point in time Remington had a recall on the trigger for the 600s .any rifle that had trigger work done by remington will have a "V" on the side of the trigger.