25' 30 amp extension cord

To my knowledge, at least in this country, (USA) both Underwriters Laboratories (UL) and the National Electrical Code (NEC) require that the number of conductors, the gauge, the material, and the insulation type be permanently marked on any electrical conductor sold here for public use in/with structures fed by public utilities. AFAIK, the same is true for attached permanent connectors. That doesn't mean that there won't be counterfeit materials that find a way here. Using reputable sources for your electrical supply needs should alleviate most potential problems because of the potential liability. It's clearly not worth it for deep pocket corporations to get caught cheating just to save/make a buck.

It just amazes me what competent professional fire investigators can figure out in the aftermath of a deadly fire.

Chum lee