Skeeter, 740 bar transducer (the same as 650 bar crusher) works fine with same loads that can be used in a 3 ton gun. When the Brits transitioned to bars, there were only two levels of proof for 12 bore guns: 850 bars (crusher), which equals 960 bars transducer, which is now standard proof; or 1200 bars crusher, which equals 1370 bars transducer, and is now superior. Can't help you with the 3 1/2 tons, which is obviously higher than 3 tons, but which is not suitable for American 3" magnum loads (that would be 4 tons).
Doubt my Italian is any better than yours, but I also interpret it as indicating that those shells should only be used in magnum/superior proof guns. If yours is 3 1/2 tons, I wouldn't use them.
