"professional duplicating film" was a single step ( negative to negative or positive to positive ) film that kodak sold but stopped making.
photowarehouse sells the same thing .. it is very slow, like azo paper,
and requires a floodlight to expose (i have used a 300W bulb) it would be between 7 and 10 stops slower than conventional photo paper, rated somewhere
between asa 6 and 25 ... and it is processed in paper developer ...
some folks have had very good results shooting the efke paper.
on the large format forum there are a handful of recent posts that look very nice.