Your wrong, Try again. Thayeri occur south of Monterrey mex. at elevation.
Alterna occur in various forms, North of Monterrey.
The name variable king is applied because thayeri are polymorphic. Which means, they have many colors and patterns.
Yours looks very much like a wild phenotype. Most on the internet are captive productions that are not phenotypic. Which means, they do not occur/survive in nature. The grey is a very common sign of age. And that animals appears very old.
My bet is, you have two retired breeders that some one is trying to recycle. The good part is, they live forever, so take good care of them.
Also check with your state wildlife laws. Alterna are of some concern in NM. Protected in some areas. My friend Charlie Painter, is the state reptile guy,(game and fish) so ask for him, hes a very good fella.
On a side note, he and I are working on a fun project together.
I think the actual point is, there is no value in rationalizing whether they are crosses, or natural crosses, or whatever. This hybrid, cross, intergrade thing is a pile of poop. Unless those animals are local specific, then they are great captive snakes. If for some reason you sell them or their offspring, then simply tell the history as you know it.
All captive snakes in the hobby are not of any local value. They are all just pet snakes. Local is important on a toe tag. That is, on preserved specimens. Or on research animals. After that, its only in hobbyists heads.
An example for those who care. Most captive local thayeri, do not represent wild phenotypic "thayeri", they have been captive bred to a point that there is no longer any phenotypic resemblence. As we are talking about color and pattern, if they do not represent what occurs naturally, then they are NOT NATURAL.