Meter-gauge modeling is extremely rare in S-scale, but there are a couple of people who are doing this. This gauge is exactly as its name implies; the gauge between the rails is exactly one meter, 100cm, 1000mm, or 3' 3-3/8" in Imperial units. It is, therefore, treated as a "narrow-gauge".
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In the real world, this railroad gauge is used just about everywhere in the world. It used to be popular in the European colonial powers, so wherever those countries (England, France, and Germany) settled, they established this rail system. Over the decades some of these have disappeared, or have been widened to "standard-gauge", but you can still find this gauge used in many countries. For a complete listing, see this Wikipedia entry.
Needless to say, there is no commercial support for modeling in this gauge in S-scale, so creative kitbashing and scratchbuilding is required. But, of course, that can be half the fun.
Marcelo Lordeiro in Brazil is one such modeler. He has a company called "MR Custom Service", which, since 1987, has been offering all sorts of model railroading services. He, himself, models in S meter-gauge, and has several pages on his business web site covering the models that he has made.