Interesting, I've never heard of this. I see an example that involves an HTTP response header "Rating: RTA-5042-1996-1400-1577-RTA". But does this actually still get used by parental controls? I didn't run into a lot of documentation about this, including on the very badly designed RTA web site https://www.rtalabel.org/

For anyone curious about the value, the numbering on the value is just a fixed number everybody decided to use for some reason that isn't clear to me.

I would deeply prefer to do it this way, but my goodness the RTA org needs a serious brush up of their web site and information on how to use this.