49 C.F.R. § 1312.7 – STB tariff designation.

(a) Format. Every tariff shall show an authorized tariff designation consisting of:
1. (1) The characters “STB”;
2. (2) The assigned alpha code of the carrier or agent issuing the tariff; and
3. (3) (i) The tariff number (selected by the carrier or agent) to distinguish that tariff from all other tariffs filed by the same issuing carrier or agent. Tariff numbers shall not exceed 5 numerical digits and may be followed by not more than 2 letter suffixes. Examples of tariff numbers are:
  STB XXXX 100 STB XX 8000-A STB XXXX 12345-AB
4. (ii) Suffixes may be used only to designate reissues of tariffs. As an example, a reissue of tariff 1000 could be designated 1000-A, a reissue of tariff 1000-A could be designated 1000-B, etc.
(b) Alpha codes. Alpha codes are assigned to carriers and tariff agents by the National Motor Freight Traffic Association, Inc., 2200 Mill Road, Alexandria, VA 22314.
(c) Fees for assignment. Fees may be assessed for the assignment of codes, but may not exceed the processing costs.
(d) Code listing. A list of the assigned alphabetical codes, and the names of the carriers and agents to which they are assigned, as well as subsequent changes to the list, shall be submitted to the Board's Section of Tariffs.