For years I said the same thing. To this day I agree with that. But i discovered the Duffeys of MD before 1820.
John, there is another Diffey from 1755 or before. John Duffey. He is on the same page in 1776 as Alexander Duffey.
This is part of the Diffeys of MD. How it fits I dont know. Its not that we are having Different ideas. Its that there is new info out there "Duffey". Maybe we can both take this lead and see what we can find.