501. Selection patents.

In the case of selection patents1 the inventive step lies in the selection, from among a known class of bodies, apparatus or processes, of some which possess a special advantage. It is necessary for the validity of a selection patent that substantially the whole of the selected group should possess this advantage and that it must be peculiar to the group, or at least be possessed by only a limited class of things outside it2. Generally also, where there is no novelty in the method of preparation, the advantage should be of an unexpected character, or otherwise not obvious

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