All picture tubes, whether monochrome or color type are identified by a specific code consisting of numbers and letters. The codes are different from each other because different tubes have different characteristics.
For example, a certain monitor colour picture tube may have designation, M34AFA63X03 that can breakdown into 6 parts: M/34/AFA/63/X/03
Part 1: Application
Computer monitor tubes start with letter "M” while for a TV picture tube, it start with “A”.
Part 2: Screen diagonal measure in centimeters (cm)
The “34” means diagonal viewing measure is a minimum of 34cm which refers to 14” tube, 36cm is 15”, 41cm is 17” and so on.
Part 3: Family code
The three letters “AFA” designate a family of tubes that have similar physical and electrical characteristic. These letters are assigned alphabetically beginning with “AAA”, followed by “AAB”, “AAC” etc.
Part 4: Family number
The number 63 shows a specific tube within family code. A different number is assigned to tubes within same family that have different neck diameters, for example a single digit would be a monochrome tube, but this two-digit number shows it is colour.