Since those 8.5V peaks / dive to 3V and then to 5v happened within 3.5ns, I dont think your SmartCard would not have come to any grief, even if you had left it at that.

OK having seen that with the sampling scope, could you manage to knock out the swing and dive from the clock pulse ?

The issue of a "CLEAN" clock pulse is inversely proportional to the sophistication level of intrumentation deployed to monitor it. Higher the level, lesser the CLEAN !

Raghu