in ArcMap 10.6.1 (using the new arcpy.mapping module NOT arcpy.mp) arcpy.mapping.MapDocument("CURRENT").activeDataFrame.referenceScale returns: u'1:{YourCurrentRefenceScale}' as a bonus: arcpy.mapping.MapDocument("CURRENT").activeDataFrame.referenceScale = "1:1000" will set the Current Reference Scale to 1000 and Refresh the ActiveView. and: arcpy.mapping.MapDocument("CURRENT").activeDataFrame.referenceScale = "1:0" will Clear the Current Reference Scale and Refresh the ActiveView.
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