Test shots on Harman Direct Positive Paper.
Quarter plate, very dull flat lighting, EV=12, Preflashed for 2 seconds (just under half the preflash that would register as a visible tone) The two exposures were identical, but the left was developed 2 mins in Ilford Multigrade, the right 2 mins in ID3. Note the image on the right has no true black, even in the unexposed borders.