Check the complete model and the certification label for its generation.
The linked 2020 Metropolitan installation manual states that the covered towel warmers are cETLus listed for use in the United States and Canada. It does not support applying a universal cULus file number to every Metropolitan model.
Use the full model on the unit and its certification label when locating a listing or preparing inspection documents. A UL-listed heating wire or control component is not, by itself, the certification of the complete towel warmer.
For dual-connection -HP models, use the separate Metropolitan dual-connection manual and the label on that unit. Do not transfer a historical file number between generations.
Sources: Metropolitan 2020 installation manual (Electrical Requirements) and Metropolitan dual-connection manual.