Try this web link for the answer to your question. http://oldguns.net/cgi-bin/f2f/f2f.pl?http://oldguns.net/q&a1_05.htm Most likely your Marlin in .45-70 Govt. is a model 1881. These early Marlins were not recoded in Marlin records prior to about serial number 4000, but your's should date to about 1882.
The value of a .22 caliber bolt action Marlin Model 20 rifle with a serial number 71377074 is between $100 and $400. The actual value varies greatly based on its overall condition and the potential buyer.
This Marlin 39A Mountie .22 Caliber Lever-action rifle with serial number R5077 was manufactured between 1957-1958.
53 years old.
The "U" prefix on the serial number means it was made in 1961.
Your marlin 336sc(standard carbine) was made by the marlin firearms company in 1950.
You would have to supply a detailed description of the rifles overall condition to get a correct value.
The J prefix to your serial number indicates that your marlin model 39A was made in 1952.
Early firearms in .22 caliber were not required to have a serial number. Your Marlin 81 falls into this time frame.
There should be a letter in front of that. That letter will tell you what year it was made.
1980
Somewhere on the frame.
1975.