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A geometric congruence class is an equivalence class of figures under geometric congruence: two figures represent the same class when a Euclidean isometry maps one to the other. It forgets position and orientation but retains lengths and angles. For example, every triangle with side lengths $3,4,5$ represents the same class, by side-side-side congruence. A mirror image belongs to the same class when reflections are allowed; restricting to orientation-preserving motions can distinguish the two orientations of an asymmetric labelled figure.