We are talking about real men flying real aircraft knowing their and their aircraft limitations.
I think most jets have a Vmo of around 300 KIAS below 10'000
No!
VMO?MMO is VMO/MMO at all altitudes.
Out of many places, break out on top, accelerate to 320kts plus and climb; delightfully exhilarating!
250kts below 10,000, as indicated, eventuated in the US of A (and the initial SID?STARS did not have 250kts speed restriction)arriving here about the same time as political correctness, metrosexuals and `Girlie Man' aviation.
When the occasion arose, 320kts plus was optimism operating performance, saved the company time and fuel too!
In another of those delightful aircraft of the time (B727) out of Canberra, late at night cleared direct to the Sydney NDB, right turn at 500' agl accelerating to 380Kts within 15 nm, 380kt climb, cruise and descnt to 15 DME, land R/w 07; 17 minutes roll to stop.
Delightful aircraft, carefree days and great crews.
DK