Labels:text | font | diagram | white | screenshot | sketch | black and white OCR: - 2 B T 1 7 8 7 0 2 6 0 2 4 7 2 N CBT 17087026 024 72N 3 4 1 ASSEMBLY PLANT CODE 2 PART NUMBER 3 DATE BUILT 4 LOOK HERE FOR LETTER P = POSITIVE BACK PRESSURE N = NEGATIVE BACK PRESSURE BLANK = PORT VALVE