We describe a class of compact G 2 orbifolds constructed from non-symplectic involutions of K3 surfaces. Within this class, we identify a model for which there are infinitely many associative submanifolds contributing to the effective superpotential of Mtheory compactifications. Under a chain of dualities, these can be mapped to F -theory on a Calabi-Yau fourfold, and we find that they are dual to an example studied by Donagi, Grassi and Witten. Finally, we give two different descriptions of

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... main example and the associative submanifolds as a twisted connected sum.