I read the 1200 as being 1200 bar proof. Multiply that x 14.5 to convert to psi and you get a proof pressure of 17,400 psi, which is in the CIP magnum (or superior) proof range. If the proof pressure were only 12,800 psi, then there's no way one should be shooting American factory 12ga loads through that gun, since those shells have a maximum service pressure of 11,500 psi.