Very strange question, however an answer from 15 years ago.
My initial DH8 (300) endorsement was conducted in the aircraft and fortunately for me, the Training Capt was a Bombardier test pilot.
In conversation one day he mentioned that during the type certification, the aircraft was in a dive at Vmo +, from memory somthing like 270 kias, with a Vmo of 242 (if memory serves), when the gear extended for no apparent reason.
Post flight inspection revealed no damage to gear, gear doors, or airframe despite the airframe being some 30 kts over Vmo, and the gear extending with a greater over-speed.