JM is Probably correct, in the “simplified drawing process”, usually combining two draws into one operation, using a “stepped” drawing die, going from one diameter, to the next, in a single pass instead of two.
This would have also used a deeper stroke drawing machine, so the “Dot” could also signify a different production Line within the RA Plant, or even a Subsidiary Plant on location or elsewhere.
The Germans especially used combined draws, reducing the four individual draws for 7,9x57 cases to two x2 ( stressed the Brass and Steel more, but for “
instant use” ammo, this was not an issue.) Also Die cost and numbers was reduced, but wear was higher ( “swings and roundabouts”)…but what resulted was increased production. The Germans , AFAIK, did not differentiate between traditional Drawing and combined drawing. But they did mark the single Berdan Drilled Flash-hole cases with a “-” ( minus sign)…