Section 6.1, Top of page 68, in UL 2601-1:

Compliance with the requirements of Sub-clause 6.1 is checked as follows:

• Inspect the presence of required markings on the outside of EQUIPMENT.
• Test the durability of markings.

For determination of durability, markings are rubbed by hand, without undue pressure, first for 15 s with a cloth rag soaked with distilled water, then for 15 s with a cloth rag soaked with methylated spirit at ambient temperature and then for 15 s with a cloth rag soaked with isopropyl alcohol. Markings shall be clearly legible after all the tests of this Standard have been performed (see Appendix C, Item C36). Adhesive labels shall not have worked loose or become curled at the edges. When evaluating durability, the effect of NORMAL USE on markings is also to be taken into account.