The serial number on a Martin guitar is accessible by looking into the soundhole and then looking up toward the neck. In addition to the serial number on the neck block, the model designation is also visible.
A Martin guitar serial number is often the best way to determine the year of the guitar, which is available on the company website. The serial number also enables guitar owners to register their Martin guitars on the website. By registering the Martin guitar, the owner may take advantage of the warranty, but only Martin guitars from the United States and Canada are eligible.