A B767 pilot reported a near overspeed of the aircraft that he attributed to distraction and a perceived lack of familiarity with a new flight instrument display caused by inadequate training.

Narrative

Just got to level off and I turned to put my departure plate in my book. The Captain said to watch the speed. I looked up to see the speed went to Mach 86 and flashed red. Somehow the aircraft had dropped out of VNAV or the Flight Level change mode with Mach as the command speed (.82) and had reverted to airspeed in knots command of approximately 300 KTS. I'm still trying to figure out what happened because I saw the Captain (pilot not flying) typing the new altitude into the CDU. If you don't have the right cruise altitude entered sometimes I've seen it drop out of VNAV. Anyway; I think we were right at VMO but did not see us exceed it (.86M). It was very odd that no clacker was heard. Maybe we were just below this speed. Contributing factor was that it was a new flat panel aircraft and it requires a completely different scan than the normal aircraft. The Mach speed you are actually flying is in very small white numbers below the speed tape. In huge font is the indicated speed actually on the tape - which is pretty useless when you've crossed over to flying Mach. It would help if a software change could switch the IAS to MACH indication at the appropriate time; like it did on the round dials we are used to. We only fly flat panels rarely and I really can't believe the FAA signed off on that or our lack of training quite frankly.