This is an out dated reference book, but is it still worth keeping as a guide? It came out in 1958 and is now almost 60 years old and is older than many forum members.
I had the pleasure of knowing Ed Simmons and seeing his LeMat collection and other collectables, he was a first class gentleman and I learned a great deal from him.
All of Bill Albaugh's books are worth owning. Yes, more information has come to light since they were pulished, but I wouldn't call them outdated. Civil War collectors, particularly Confederate collectors, owe a great deal to Bill Albaugh. Some of us had the pleasure of knowing him.
Some additional information has come to light in the years since those were written, for example specifics on the firm of S. Isaac, Campbell & Co. Those books are still excellent baseline research.