I was told by Les McLean that there was a time when Ilford used to make thier paper sample packs that went out to thier dealer sales points by contact means. Thousands of prints of each image would be required.
Enlarged negatives were used, and contact printed. If there were any areas that needed burns or dodges, then the effect was replicted by strategically placing bits of neutral denisty acetate on a diffusion layer in the opticla path between the light source and the negative. Then the thousands of prints could be banged out by anyone working the contact printer.
I have also seen on the *bay old contact printers with banks of individual lights that colud be selectively turned on to give the same effect by varying the intensity of the lighting source, so it vared across the neg.