According to 505.9(C)(1), "Equipment identified for Class I, Division 1 or Class I, Division 2 shall, in addition to being marked in accordance with 500.8(B), be permitted to be marked with the following:
Class I, Zone 1 or Class I, Zone 2 (as applicable), and
Applicable gas classification group(s) in accordance with Table 505.9(C)(1)(2), and
Temperature classification in accordance with 505.9(D)(1).
The additional markings are permitted, not required, but in order to use the equipment in a Zone-classified area, the equipment must use an acceptable protection technique and be marked according to 505.9(C).