 These designs were either difficult or impossible to find using 1940s metal detectors.Many different types of minimum metal mines have been produced in various countries over the years.Relatively modern examples include the antitank mines M19 (United States, less than 3g of metal) and TMA-3 (Serbia, no metal) and the anti-personnel mines PRB M-409 (Belgium, less than 1g) and the PMA-2 or PMA-3 Serbia, (approx 1g non-magnetic) and VS-50 (Italy).