250 below 10k: try this
Origin of the 250 knots below 10,000 ft rule [Archive] - PPRuNe Forums
In ICAO airspace? Yes and no, depending on the class. A, B, C: no speed restriction. D, E, G: max 250 below 10k. Don't know about F, but I assume it's also 250/10k.
That said, speed restrictions are sometimes imposed regardless of the airspace class. I think the Yanks are 250/10k regardless.