MT4 uses a broker plugin, and its manual page explicitly says whether to use the NFA flag.

You would know if you were the one programming the window controls. The only one that I am aware of is for a fake website:
https://financial-hacker.com/binary-options-scam-or-opportunity/

Do you have any real examples?

Any time!

Thanks AndrewAMD. Yes, the MT4 page has info, but it also talks about (at least 1) error message one will get if the setup is wrong for a particular broker. I'd prefer to trade error-free!

No real world examples (yet) - trying to wrap my head around this world of US restrictions... Without losing everything in the process...

Thanks.