These eyes were just cut with a chisel,or a bench knife would do.
In English planes,I think the most beautiful eyes evolved in the 19th.C.,on coffin smoothers. They got larger,and their sides just blended with the curve of the sides. I know there is a picture of a coffin smoother I added an iron sole ahead of the blade to. It has beautiful eyes. I'll try a search. Not sure if the eyes are seen in those pictures or not.
P.S.: Search for "a very nice apple wood plane" It has nice eyes,larger,and more developed than these here.