They add no quality to the database.
They do for someone wanting to know where the historic boundaries lie.For example in cross-referencing the old OS County Series maps, see for example:
https://maps.nls.uk/view/121856992#zoom=3&lat=8515&lon=14122&layers=BT Martin. _______________________________________________ Talk-GB mailing list Talk-GB@openstreetmap.org https://lists.openstreetmap.org/listinfo/talk-gb
