Datamax M-Class Mark II M-4206 - Manual (Page 40)

34 M-4206
The second label printed is the Dot Check Label. This label is used to test the condition of the printhead, as shown below:
Good Dot Check Label:
Even pattern consistency
indicates that the printhead
is operating normally.
Faulty Dot Check Label:
Streaks in the patterns
indicate a dirty or faulty
printhead (see Chapter 5).