(a) Each applicant for a tankerman-engineer endorsement must present evidence of at least—

(1) 90 days of service as an engineering officer on tankships or self-propelled tank vessels certified to carry DL or LG appropriate to the endorsement applied for;

(2) 90 days of rating or cadet service in the engine department on tankships or self-propelled tank vessels certified to carry DL or LG appropriate to the endorsement applied for; or

(3) A combination of the service in paragraphs (a) (1) and (2) of this section.

(b) Each applicant already holding an MMD or MMC endorsed as tankerman-engineer for DL and seeking an endorsement for LG, or the converse, must prove at least half the service required by paragraph (a) of this section.