Reminds me too ... a bit sad.
The BA Concordes, in the front of both cabins, had a nice display showing Mach, altitude, ground speed, etc.
Of course, once at Mach 2, everybody wanted their photo taken next to the Machmeter.
Unfortunately, the display was a pale yellow (backlit LCD, IIRC) with a protective plastic cover.
You can guess the rest.
An untold number came home, from what for many was a once-in-a-lifetime never-to-be-repeated flight, with a nice photo of themselves .... next to a brilliant reflection of the flash, which had totally washed out the coveted "Mach 2.00"....
CJ
PS : the French Concordes had an old-style Mach-number-only display (EL or plasma, not sure) but much brighter, so the problem didn't occur there.