((a)) On application by the owner and approval by the Secretary, the tonnage of spaces prescribed by the Secretary may be excluded in measuring under this section the gross tonnage of a vessel measured under . The spaces prescribed by the Secretary shall be comparable to the spaces that could have been excluded under (, ), as section 2 existed immediately before the enactment of this section.

((b)) The Secretary shall prescribe the design, location, and dimensions of the tonnage mark to be placed on a vessel measured under this section.

((c))

((1)) If a vessel is assigned two sets of gross and net tonnages under this section, each certificate stating the vessel’s tonnages shall state the gross and net tonnages when the vessel’s tonnage mark is submerged and when it is not submerged.

((2)) Except as provided in paragraph (1) of this subsection, a certificate stating a vessel’s tonnages may state only one set of gross and net tonnages as assigned under this section.