I am trying to find more information on Culuert mac Donnchad. I have a rough copy of a Latin land document (dated 1095) executed by Duncan and witnessed by Culuert son of Duncan. My mothers' family name is Culbertson and claims direct descent from the original Culuert. According to family history, When Duncan was murdered, Culuert went to Northern Scotland along with the Duncan, Malcolm and Keith families. And took along with him what is purportedly the Royal Seal of Duncan mac Crinin which had been passed on to him. It is a round cornered rectangular amethyst, finished flat on top and bottom, about .5" by .75" and .375" thick. On top it is carved intaglio with a blue bell thistle centered and surrounded by the words AE GOODTURN DESERVS ANITHER. The seal has been passed down through the Culbertson family to this day. Some time during the mid1800s the stone was mounted in an historically correct gold ring setting.
If anyone has come across anything in your researches I would appreciate hearing about it.