I got off on a tangent and started trying to find the original RMS standard (USA FTC) for amplifier wattage. There seems to be a agreement on 90% of the standard but then there's some hearsay. Here's the actual 1974 standard, 39-FR 15387 https://www.ecfr.gov/current/title-16/chapter-I/subchapter-D/part-432
The USA FTC did publish a 19 page "Final Rule," I can't find the date but it was after 2023. https://www.ftc.gov/system/files/ftc_gov/pdf/amplifier_rule_-_final_rule_notice.pdf "Although commenters overwhelmingly supported the Rule, some recommended amendments. For example, many commenters urged the Commission to require uniform power band, load impedance, and THD limits to prevent manipulation of these three test conditions.14 Consistent with these comments, FTC staff found such manipulation ubiquitous in the marketplace. Specifically, FTC staff found dozens of examples of the same equipment advertised with significantly different power output claims" I don't know what happened in the 80's but we started seeing boomboxes (and component/car audio) go from a few watts to hundreds and even thousands by manipulating the testing methods and using terminology other than "RMS." I'll post more when I dig it up, feel free to contribute.
