Interesting Flag Signal Instructor. Sliding dial shows different flag configurations for different letters in US Army and Navy semaphore code. Patent information from Great Britain and United States are on the sides but the US side does have some small flaking (See photo). The reverse shows International Morse code with one flag or lantern with some further instructions on semaphore code on the bottom. Communications have become increasingly important with armies and methods of communication are always being developed and refined. I think maybe the semaphore code was used when the mustard gas interfered with cell phone tower transmissions, but I may be wrong on this last point. Nice little remnant from WWI in good shape for its age and construction.