For a description of various Underwriters Laboratory markings in the US and around the world please see -
I have copied and pasted the section for North America here. Note that the term Listed is critical - compliant and other terms have no meaning as far as I can see. Often people try to play with words to make potential customers believe unlisted products carry the same seal but that is generally not true.
UL Listing Mark
The UL Listing Mark is one of the most common UL Marks. If a product carries this Mark, it means UL found that representative product samples met UL's safety requirements. These requirements are primarily based on UL's own published standards for safety. This type of Mark is seen commonly on appliances and computer equipment, furnaces and heaters, fuses, electrical panel boards, smoke and carbon monoxide alarms, fire extinguishers and sprinkler systems, personal flotation devices, bullet resistant glass, and thousands of other products.
There are three variations of UL's Listing Mark: one used only in the United States, one used only in Canada and one for both the United States and Canada. The C-UL Mark is applied to products for the Canadian market. The products with this type of Mark have been evaluated to Canadian safety requirements, which may be somewhat different from U.S. safety requirements. The optional C-UL-US Mark indicates compliance with both Canadian and U.S. requirements. UL encourages those manufacturers with products certified for both countries to use this combined Mark, but they may continue using separate UL Marks for the United States and Canada.
The UL Listing Mark appears on end products and complete components suitable for factory and field installation. All of the products carrying a UL Listing Mark are covered by UL's Follow-Up Services program to verify that end products and components carrying the UL Listing Mark continue to be manufactured in compliance with UL's safety requirements. A UL Listing Marking appearing on a product typically consists of four required elements:
- "UL in a circle" symbol
- Word "Listed"
- Product name or company name/file number
- Issue/serial number or alphanumeric control number