Motosacoche was a Swiss motorbike brand from Geneva. They also made engine blocks for other motorbike brands, which they could not sell under their own brand name. That's why these blocks were given the name M.A.G. which means Motosacoche Acacia Geneva. This was simply their address. These engines were known to be fast and solid and were used with most other motorbike brands. This is a 500cc OHV sports block with dual exhaust.

Motor is loose.