Re: It's a hand hole, isn't it?
Actually w/ wood as thin as wood used in inner cover construction I would imagine a bit and brace and a sharp knife would have been used, not a saw. That's how I woulda done it. Proper grain orientation would have been crucial.
In the mid19th Century sets of bits were quite common, coming in a variety of sizes. What you illustrate is very 1940s up to today, I believe.
Just because something is new to you, doesn't mean it is new, or revolutionary. Mark Berninghausen