H prefix indicates 1951 mfg.
1950.
1949
Your marlin 336sc(standard carbine) was made by the marlin firearms company in 1950.
your marlin model 336sc(sport carbine) was made in 1951.
Your Marlin model 336sc(sporting carbine) with the letter prefix of G indicates that it was made by Marlin in the year 1950.
1958 to 1960
The serial number prefix letter of G indicates that your Marlin model 336SC(sporting carbine) was made in the year 1950.
The model 336SC was manufactured from 1949 to 1963.
1950
Your marlin model 336 sc (sport carbine) was made in 1953.
R date code is 1957-58. Kim Hayes
You're probably better off sending an e-mail to Marlin. Also, posting firearm serial numbers on the net isn't a good idea.