The telegraph was the only long distance instant communication device until radio and other means came along. Railroads were always the largest users of the telegraph and utilized them for more than a century. The railroads would have had a very hard time operating safely and efficiently without them.
The full size plans will allow you to make an exact replica of the key and sounder. The photo above is the "real thing" antique originals. The originals were made in a time when quality was of prime importance and aesthetics ran a close second! These instruments were made of brass and steel, as were all manner of other types of instruments. You will want to make yours of these materials as well.
You can make an operating set, or as non-operating shelf models. Either way, you can make them full size or reduce the size for really neat items to put in your curio cabinet or as a unique desk ornament set.