That is correct- in 1878 to whenever WRA dropped the High and Low Walled single shots- mild lower carbon resulpherized steel was used for the forgings- and that analysis would take bone case color hardening with good results (if oxygen was NOT allowed to contaminate the vessel during the pour in H2O--
I am just 'spitballing here" but as the japanese have, since post WW2 rebilding- Electric melt furnaces- and also import all of the ores used in modern steel making, you are looking at possibly a forging (or lost wax investment casting) with; higher points of carbon, also nickel in a higher content range, silicon, chromium, molybdenum and even possibly vanadium. All of which could affect the outcome of the old charcoal and bone meal 'packing box" color case hardening.
I have seen several examples of Doug's fine work- if I wished to have a modern weapon, no matter where in the World it was made, changed from a blued finish to color case- Doug would be my first choice-