I believe Remington took over Marlin in January 2008 and Marlin stopped production of the 336 30-30 at the end of July 2010 (but it may have been first of August). So, if you want a (non-Remington) Marlin 30-30 you need to confirm it was made prior to 2008 and if you want a Connecticut (but still Remington owned) made Marlin you need to confirm it was made before August 2010.
All Marlin's manufactured after August 8th or so will be from New York.