Nice find. Are you sure it's not 1/4-inch hex drive?
Very illustrative of the style and construction. Most examples are not so completely denuded of its characteristic copper coating, but rare is the set with it all intact.
Typically, neither the sockets or the handles in the "A" (1/4-inch hex drive), "C" (7/16-inch hex drive) and "C Special" (7/16-inch hex drive with special ratchet) sets had markings of any kind, branding, COO, or sizes.
The ratchet in the "D" (1/2-inch hex drive) and "G" (1/2-inch hex drive with special sockets) sets was branded, the sockets typically have sizes, but no branding, although there is a cool rather unique "D" set on the Bethlehem thread here where the larger sockets with more real estate are branded.
The "F" (11/16-inch hex drive) set handles are branded, the sockets had only sizes.
We don't know about "H" (unknown), "K" (1/2-inch square drive), or "XF" (1" square drive), no sets have been found in the public domain.
If you're interested in other examples and further reading, we have a thread easily accessible from the A-Z Index of Threads in the Sticky...