Despite their name, historic counties do exist in the present day. And distinguishing them from ceremonial counties is not rocket science.
For instance:
- Greater Manchester is a ceremonial county. Most of its area is within the boundaries of the historic county of Lancashire, with the part south of the River Mersey within the boundaries of the historic county of Cheshire.
- Westmorland is a historic county. Its entire area is within the boundaries of the ceremonial county of Cumbria.