(a) Each tank car must be marked according to the requirements in appendix C of the AAR Specifications for Tank Cars (IBR, see § 171.7 of this subchapter).

(b) Each tank car that requires a tank-head puncture-resistance system must have the letter “S” substituted for the letter “A” in the specification marking.

(c) Each tank car that requires a tank-head puncture-resistance system, a thermal protection system, and a metal jacket must have the letter “J” substituted for the letter “A” or “S” in the specification marking.

(d) Each tank car that requires a tank-head puncture-resistance system, a thermal protection system, and no metal jacket must have the letter “T” substituted for the letter “A” or “S” in the specification marking.

(e) Each tank car manufactured after March 16, 2009, and before December 28, 2020, to meet the requirements of §§ 173.244(a)(2) or (3) or 173.314(c) or (d) that is marked with the letter “I” in the specification marking, following the test pressure, shall be re-marked with the letter “W” with a delimeter of letter “H” at the tank car's next qualification. (Example: DOT 105J600I would be re-marked as 105H600W.) Each new tank car manufactured after December 28, 2020 shall be marked with the letter “W” following the test pressure and with a delimiter of “H”. (Example: 105H600W).