Margery, Dewar is not a Manx name but the IGI gives Jas (James) Dewar and Elizabeth Corkhill (this is a Manx name!) having a child, Jane, in Onchan bp 26 April 1807.

An Elizabeth Dewar is married in Braddan in 1833 so probably bn about 20 years previous.

So wonder if this is a possibility of Mary's family? Unfortunately there are no other baptisms to Jas & Eliz Dewar listed but maybe worth checking the original baptism registers for say Onchan/Braddan.......

Brian Lawson's site (www.lawsons.ca ) gives a Donald Livingstone Dewar buried in Douglas in 1925, and with a name like this, suggests Scotland to me.

Also at Brian's site, in the marriage index there is an Alexander Cumming Dewar marrying in 1890 to a Mary Warburton.

So the name Dewar was on the IOM, but few in number.

Elizabeth