The Dews surname does not have a coat of arms.Only individuals can have coats of arms.
More information on this subject can be found at http://www.sog.org.uk/leaflets/arms.htmlhttp://www.sog.org.uk/leaflets/arms.html, The Society of Genealogists Leaflet, #15, "The right to arms", which explains: 'Coats of arms and crests are a form of property and may rightfully be used only by the male-line descendants of the individual to whom they were first granted or allowed. Such grants were and are made by the appropriate heraldic authority acting under the sovereign.' Which is to say, a coat of arms does not belong to a surname, but to an individual.
It's a good read. Also, these businesses that sell coats of arms and tartans with a claim to represent some family name are selling a mostly false bill of goods rather than anything to do with accurate family history.
These faux coats of arms look nice but they have no historical nor genealogical value.