We have spent years working through the Coast Guard's rules and the US Code of Federal Regulations so that you never have to. If you would rather go to the source yourself, these are the ones we use every day.
If you would rather work it out yourself, this is where we go. No login, no charge, straight to the Coast Guard.
The USCG National Maritime Center →USCG Policy & Regulations →46 CFR PART 10: MERCHANT MARINER CREDENTIAL →To clear up a common misconception, your documents are not kept at the NMC but instead sent to the National Archives after your license has been issued.
To get them back from the archives takes a little while but is pretty easy.
First: Fill out the Correspondence Request. Pro-tip: Select "Copy of Entire Record"Second: Print it, Sign it and Scan it
Then Email it to: OSC-SMB-NMC-4-Correspondence@uscg.mil
It will take a couple of months but out of the blue you will get a package in the mail!