You can use this tool to date any C.F Martin guitar from its serial number. It can accurately date any Martin guitar from 1898 to date. Earlier Martin guitars will be shown as pre-1898. I also have a tool to decode C.F. Martin mandolin serial numbers
The serial number on Martin acoustic guitars is below the model designation on the end of the neck block inside the guitar. It will be a number between 4 and 7 digits long.