(1) A reference in this Subpart to a fireproof manufacturer's data plate is a reference to a data plate that:
(a) is made of material that withstands the heat of a fire at least as well as a steel plate of the same size and thickness; and
(b) on which the details that it is required to bear are legibly marked by a fireproof method.
"fireproof method" of marking means marking by:
(a) etching, stamping or engraving; or
(b) another similar method of marking approved for a particular
purpose.