If it helps, I've been using the 10073 series probes for many years. The 10073C scope probe isn't a 10Meg probe, it's more like 2.2Meg. Try measuring it (with a DMM set to ohms) with it connected to a regular 1Meg scope input.
I think you will see 2.2Meg and not 10Meg.
Also, try compensating the probe and have a look at the shape of the leading edge on the scope display as you adjust the compensation. On the scope display a?10073C will look very different to a run of the mill x10 scope probe when adjusting the compensation. The leading edge of the waveform should be much, MUCH 'tighter' with the 10073C. This is another signature for a genuine 10073C.
You can also try measuring the rise-time of the probe?
