46 CFR §13.505

1. (a)Provide evidence in a method prescribed by the Coast Guard of proof of service from the owner, operator, Master, or Chief Engineer of a tankship or self-propelled tank vessel. The evidence must specify—
   1. (1)The classification of cargo (DL, LG, or both) carried while the applicant accumulated the service; and
   2. (2)The number of days of officer, rating, and cadet service in the engine department on tankships or self-propelled tank vessels; or
2. (b)Service must be proved by certificates of discharge from tankships or self-propelled tank vessels with the appropriate classification of cargo (DL, LG, or both).