It's a 'saw wrest', and it is indeed for setting saw teeth. Some, as this one, also had a screwdriver built in to tighten handle screws. They were rather superceded by the various pliers-type saw sets, but still appeared in the catalogues until quite late on.
(Edit to add - It may have come to light in Spain, but a pound to a pinch of **** it was made in Sheffield.)