Had my first few in Texas many years ago at a restaurant where you raised a flag if you wanted the waiter to come by (El Paso?). Anyway, they are hard to find in Delaware
Ahh Pancho's Mexican Buffet. Cheap mediocre food and the only way to get service was to raise that little flag.
They are located only in the Southwest, and their numbers are dwindling. But they have been around for many many years.