[Hugh]

Here  is the up to date list of all early U.S. covers. U.S. Scott #1 up to over  #500 U.S. stamps used on cover and who found them.  

Thanks for posting this Richard. It's a great resource. I have Sampson's American Stampless Cover Catalogue (bought it at the Club recently from Mark). It's also good, but I like that fact that since your document is a PDF, it's very easy to do a quite digital search. 

Cheers, Hugh