The Copt Howe one is almost certainly a bullaun (obviously without actually seeing it first hand I can't say for sure, but it looks quite classical)

The smaller one fitz showed us is probably the Neolithic fore runner, which are very rare indeed. In fact they are so rare no one's really acknowleedged tham yet and still date bullaun as Bronze Age onwards. This one is rough and so could be a pestle rather than a water collecting bullaun, which are nearly always hemispherical. I know of one conical one ...

There are a lot of theories out there, but no one has done a proper study of them yet. I'm trying to get my head around them, but with many being moved to church yards it makes it very hard. And then you discover that there are over 100 on Gottland and 'some' in Lithuania and one in Cumbria ... oh hum. I know of a priest in Gottland who's cataloging all the ones there, when he's finished I might go over and see them ( a fine excuse to go there and see all the other wonders I'd say :-)