Before I go any further, let's get this detail out of the way: While the recipe title ("Creamed Chipped Beef on Toast") is the "official" name for this dish, it is much better known (especially among our veterans) by the more colorful names "$#!& On A Shingle", "Same Old Stuff", or simply SOS. Choose the one that best fits your personality or the company you're feeding, and let's continue. :)
For many, their first exposure to this dish was through the military, with its first known published appearance being in the official Army Cookbook in around 1901. It also is well known among our older generations as being something that was simple, quick, relatively inexpensive, filling, and versatile (as it can be served for breakfast, lunch, or dinner) - a great combination when you're living in hard times.
These days, it's still a great comfort food... but with the changing times, sometimes allowances have to be made. For example, for many years dried beef packed in salt was used as it was a commodity item produced in large quantities due to its ability to be stored for long periods of time without any special considerations. Today, modern refrigeration has almost completely eliminated the market for dried beef, so it's sold more as a specialty meat at a premium price. The closest substitution (and what was used here) is thinly sliced sandwich meat found in the refrigerated deli section of a local grocer. The one advantage to this is much less salt is used than in dried beef, which makes it better for those who are watching their sodium intake.
Note that there are several variations found all over the place that often focus on seasonings for the gravy; it can be a bit bland, but thinking back to when it was first made the concept of using lots of varied seasonings was not well established. I've added a little bit to this version, and I'll list several suggestions for other seasonings in the notes at the bottom of the recipe card.
Adapted from The Country Cook