You guys beat me to it.
I was thinking about this last night and I think we're chasing a ghost here.
I'm sure they used some base boot. But then all the custom work was done. Then a new sole was put on. The reason I think this is true, is because after all the extra leather was added to the surface of the base boot, it still tucks into the sole. If it was added to the surface of the boot with the sole already attached, there would be an edge where the leather meets the sole.
So to replicate these boots, here's what I'm thinking.
*Find a base boot that matches what we can see, mainly the eyelets.
*Have the sole removed.
*Add all the custom leather work.
*Have the correct sole attached.
The other option is to add the custom leather work to a boot that looks right and forget about the sole.