CM Attribution Type (CM Model) is a Dimension in Google Analytics under the DoubleClick Campaign Manager section
CM Attribution Type (CM Model) Definition: There are two possible values: ClickThrough and ViewThrough. If the last DCM event associated with the Google Analytics session was a click, then the value will be ClickThrough. If the last DCM event associated with the Google Analytics session was an ad impression, then the value will be ViewThrough (Analytics 360 only).
Web Analytics & Insights Google Analytics Dimensions CM Attribution Type (CM Model)