According to AWS 5.1-91 Part C Sec. 22 Electrode Identification
paragraph 22.1
At least one imprint of the electrode designation (classification plus any optional designators) shall be applied to the electrode covering in the order specified in Figure 16 (i.e. EXX YY-XXX)within 2-1/2" (65mm) of the grip end of the electrode.
Paragraph 22.2
The numbers and letters of the imprint shall be of bold block type of a size large enough to be legible.
Paragraph 22.3
The ink used for imprinting shall provide sufficient contrast with the electrode covering so that, in normal use, the numbers and letters are legible both before and after welding.
Paragraph 22.4
The prefix letter "E" in the electrode classification designation may be omitted from the imprint.
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