After the proof house revisions of 1924, a Certificat d’epreuve could be issued and specified:
“The pressure developed, measured by crusher type device, lower or equal to 600 kg per square centimeter for sizes 16, l2, 10, 8 & 4; 670 kg per square inch for sizes 20, 24 and smaller.”
600 kg/cm2 = 8534 psi maximum SERVICE pressure;
670 kg/cm2 = 9530 psi maximum SERVICE pressure
+ 10 - 14% by piezoelectric transducer measurement
20 g was PROVED at 1000 kg/cm2 = 14,223 psi
12g PROVED at 900 kg/cm2 = 12,801 psi
Modern transducer numbers for 20g would be close to 15,500 psi; 12g about 14,000 psi
