I have two "Bluegrass Fakebooks" - the words and chords only and apparently "home printed" kind, both of which show Gold Watch and Chain as by A.P. Carter.

I'm not sure I'd trust either of these as being "reliable sources," but Beppe Gambetta includes the tune on his Dialogs CD, and also credits A.P. Carter.

Of course, this doesn't necessarily mean that A.P. didn't lift it from something earlier.

John