The Excelsior Hive Cover

While scanning Garreson Publishing's website I noticed that the book Making the Eight Frame Hive had plans for an Excelsior Cover. What is an Excelsior Cover? Nothing came up on Google except a reference to this book and some unrelated stuff. Here's what the author says<>: “About a hundred years ago, A.I. Root Company used to sell the once popular Excelsior cover. The original design required a minimal amount of lumber but required specialized equipment to manufacture.The design covered in the book can be made with a small planer and table saw. It’s cute, quaint and works well but needs to be kept painted because it is all wood. The book also shows how to make a telescoping cover which will probably last longer.”
There is a drawing on the book cover at the above site.