I upstate NY, we used to call them "KAPL KATS" (pronounced cappul). KAPL - Knolls Atomic Power Laboratory. They used to build the nuclear reactors for subs and Aircraft carriers.
We had 2 cats like this. One was similar to the above, with about 7 toes, really extra toes and pads. The other simply had thumbs, a single toe off-set like an opposable thumb.
I always thought that the ones with the "double feet" might have an advantage in the snow.