You may well have seen these in your genealogical quest. You find an ancestral home (it doesn't have to be a castle; it can be a much more humble dwelling) and, across the lintel of the main door, or across the fireplace, is a carving of a date. It sometimes includes the initials of the husband and wife who lived there, and it usually shows the date of the completion of the building.
There was one in Emily Bronte's Wuthering Heights - do you remember? When Mr Lockwood first comes across the Heights, he sees
showing that he had come across a datestone. It was fashionable from the 16th century to put up such a stone, but they are not always reliable as a source, because they may have been re-used in rebuilding or extending.a quantity of grotesque carving lavished over the front, and especially about the principal door; above which, among a wilderness of crumbling griffins and shameless little boys, I detected the date '1500' and the name 'Hareton Earnshaw' [Chapter 1, Wuthering Heights]
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