I can find Rebecca as Archibald's wife on a search of Ancestry - but I did not see a source.
In Family Search I found A.E. McPhail in a census and the wife listed is Margery.
There does not seem to be much sourcing that can easily be traced on Ancestry, FamilySearch, or WikiTree. Do you have a source for Rebecca?
This is an interesting puzzle, but I cannot follow it right now, babysitting for a 6 year old!
