Worcestershire (County), England, UK

The ancient historic county of Worcestershire as it stood at the date of the earliest brass band contests (i.e. after the reforms of 1844) took in a number of areas that are not included in the modern county of the same name.

Shipston-on-Stour was an exclave of the county until 1st April 1931, when it was transferred to Warwickshire. At the same time land around Redmarley D'Abitot was transferred to Gloucestershire.

Dudley was an exclave of the county until 1st April 1966, when it was transferred to Staffordshire. This exclave was expanded in size in 1926 to take in town expansion to the North.

On 1st April 1974, the central and Southern parts of the county were merged with Herefordshire to produce the county of Hereford & Worcester.
The Northern portion became part of the new county of West Midlands.

On 1st April 1998, Herefordshire and Worcestershire were separated again, with Worcestershire regaining those areas that had previously belonged to it with the exception of territory now in the West Midlands county.

These are not the only relevant changes in the convoluted history of this county boundary. See https://en.wikipedia.org/wiki/List_of_Worcestershire_boundary_changes for more details.