Hi Steve,
I think that the border moved at some stage. I have relatives that were born in Ilkeston Derbyshire in 1892 and the area was recorded as Ilkeston, Nottinghamshire.
Yet now - if I want to look up any information about them - I have to refer to Derbyshire records.
Confusing, I know, but I am sure that with a little research you could find out the year that the border 'moved'
Elaine