UL Label 2 : A label affixed to a product designating that it, or a prototype of it, has been tested by Underwriters Laboratories Inc. and found to be safe for general use
Ralph W. Burklin & Robert G. Purington, Fire Terms: A Guide to Their Meaning and Use, National Protection Association, Boston, MA 1980 USA. (Guide: Meaning and Use, Nat Prot Association Fr Srvc - Amer) {457}