MILL NUMBERS Grading Gradestamps on lumber are used to identify: The grading agency to which the mill belongs. The mill number of the manufacturer of the lumber The species of the lumber The grade of the lumber Moisture content at time of surfacing HT designation if applicable a) Trademark- indicates identity of agency quality supervision b) Mill Identification- product manufacturer name, brand or assigned mill number c) Grade Designation- grade name (number or abbreviation) d) Species Identification- name or abbreviation of individual species or species combination e) Condition of Seasoning*- moisture content classification at time of surfacing S-Dry- 19% maximum moisture content MC15- 15% maximum moisture content KD- kiln dried to moisture content indicated in grading rules S-Gm- over 19% moisture content (unseasoned) *HT- designation for Heat Treated- while not  seasoning designation, the abbreviation HT may be found in conjunction with the above seasoning abbreviations.  The HT definition can be found in the grading rules. Here are links and/or PDF files for the primary grading agencies for the products Arling Lumber distributes: Timber Products Inspection (TP) Southern Pine Inspection Bureau (SPIB) Council of Forest Industries (COFI) West Coast Lumber Inspection Bureau (WCLIB) Canadian Lumbermen’s Association (CLA) Alberta Forest Products Association (AFPA) Western Wood Products Association (WWPA) Ontario Lumber Manufacturers Associations (OLMA) Pacific Lumber Inspection Bureau (PLIB)