According to a case historian, this fine plow was made unchanged from 1877-1928 by J.I. CASE Plow Works.
I've noticed that this is the same as Laura Ingalls Wilder's father's plow in the museum (Little House on the Prairie).
This, of course, is in far better condition having the original finish, CASE stenciling & decals.
It seems unbelievable that this plow exists in this condition, but here it is.