That style of hook is often referred to as a “blind eye” hook. Traditionally, the material used to make the loop is silk gut. Mono can also be used to make the loop, but mono is more of a challenge to ensure it is well attached to the hook shank to avoid it pulling out while fighting a fish.
You’ll still see blind hooks used by some traditional style salmon fly tyers, especially for flies that are intended for framing. There are many salmon fly videos that show how the technique is done.
Those are some cool flies, especially, since they were your father's flies. You'll find similar patterns if you search under the category "Wet Fly" patterns.
Fly Fishers International certified casting instructor