What Firmware Can Do For You: That’s The Difference Between The EOS 1D C and EOS 1D X | CanonWatch

Canon confirmed me today the 1D C 4K DSLR is a 1D X with a firmware update. Identical hardware. [...] I also had a impromptu talk to a Canon Europe product manager who was very open and honest about Canon’s approach with this camera.

The 1D C is a 1D X with a 4K firmware update. Canon’s man told me that the only hardware change was to do with the flash sync jack (or one of the other jacks if my exact memory fails me). So essentially the 1D X hardware – sensor, processor, everything – is capable of 4K video, 100%, no heat or bandwidth issues either.
I jeszcze to (czyli tak jak z olejem opałowym - przestępstwo skarbowe?):
The tax issue [in UE] is that the 1D C is classed as a video camera, at a much higher import tax tarrif to the 1D X. Any firmware update that would turn a 1D X into a 1D C would not go down well with the tax people.