If you review the General Requirements referenced in ASME SA 516, you will find your answer below;
13.1 Required Markings:
13.1.1 Except as allowed by 13.4, plates shall be
legibly marked with the following information: applicable
ASTM designation (see 1.1) (year of issue not required);
“G” or “MT” if applicable (see 13.1.2); applicable grade,
type, and class; heat number; plate identifier; and name,
brand, or trademark of the manufacturer (for plates produced
in discrete cut lenghts of flat product) or the processor
(for plates produced from coil and for subdivided
plates (see 13.4)).
13.1.2 Plates that are required to be heat treated,
but have not been so heat treated, shall be marked by the
manufacturer or processor with the letter “G” (denoting
green) following the required ASTM designation mark,
except that “G” marking is not necessary if such plates
are for shipment, for the purpose of obtaining the required
heat treatment, to an organization under the manufacturer’s
control. Such plates shall have been qualified for
shipment on the basis of test specimens that have been
so heat treated. Plates that are required to be heat treated,
and have been so heat treated, shall be marked by the
party that performed the heat treatment, with the letters
“MT” (denoting material treated) following the required
ASTM designation mark.
