I have a mod. 336 30/30 that confirmed serial through Marlin Firearms. The serial located on tang directly under hammer.
With the serial number that you provided,your Marlin model 1893 rifle was made in the year 1899.
Your serial number indicates that your Marlin model 30A was made in the year 1979.
By including the serial number in your question,we will be able to answer when your Marlin model 336 was produced.
2.50
Your Marlin model 30AS was made in the year 1984.
Made between 1936 and 1945
Marlin
The R prefix to your serial number indicates that your Marlin model 336 rifle was produced between 1957-1958.
Model variation
30
100-400 USD
there is a marlin collectors site or gunbroker.com