C A V manufactured the Roosa Master injection pump as the D P A (Distributor Pump A )
Being an American design, all the dimensions were Imperial.
But C A V started by making Bosch pumps, under licence, pre WW2, so always worked in Metric.
The threads on the DPA were Unified, but the drawings for parts were Metric. As an instance, the Plunger in the Endplate, that regulated the transfer pressure, was 6.354 mm diameter!
At least the plungers were Metric, from 6 mm upto 10 mm in 0.5mm increments.
So we tended to think in whichever system seemed best suited to the task in hand.
Howard