Okay Michman,
I have Doug Murray's book, "The 336, a collector's reference on the Model 336 Marlin" in front of me now. You can order it from him at 20 Polo Lane, Westbury, NY 11590.
Anyway, the first year of manufacture for the 336 was 1948 (prior to that it was the model 36) so you have one of the first of the model. It came out in .30-30 and .32 Winchester. Four versions were made that year. There was the carbine with micro-groove rifling, the 336-SC or Sporting Carbine with Ballard rifling, the 336-A rifle with 24" barrel and Ballard rifling, and the 336-ADL which was the same as the 336-A but with checkering and a sling w/ swivels.
Hope this helps. Good luck in your search!
-Winter Hawk-