Update to this thread: The DWP 510 and DWP II were stored for decades in a barn in NE Tennessee; I bought them with other equipment including Model IIs and drive bays etc. and hauled them back in the van. The DWPs seemed so stiff and dirty that I didn't dare to power them up. I did a little cleaning and lube and inspected the daisy wheels to see if they were perhaps compatible with some Silver Reed wheels that fit other daisy-wheel printers. Alas, no.
Unsure of what I was looking for in the way of ribbons and wheels I posted here; my thanks again to shank and Eudimorphodon, Patrick B. and Agent Orange for your help. But the DWP II sat untested for the interim, until today when out of curiosity I powered it up. No smoke - that's always a good sign - and the whir of a fan coming up to speed as the printhead returned to the left margin. I figured it might be time to find a manual.
I got some greenbar paper loaded and powered up again, using the printwheel and ribbon that had been in the machine. I performed the self-test as described in the manual, and after a little fiddling with the "test" switch the printhead began to move. Nothing printed at first but after a few lines I began to see characters and after 15 or 20 lines the output was quite good - except for the fact that capital N was missing. Turns out it had broken off; lower-case n was still present.
Without exaggeration I can say that I was stunned; that after sitting for maybe 35 years in a barn this beast was still producing output. Not laboring, either: this damned thing is fast. Next we'll have to see if it communicates with a PC. Assuming it does, the DWP 510 and Line Printer VI are next up for inspection.
Thanks again, persons, for all your help.
-CH-