The example below is PP36c a 1d. lake-red (SG 43 or G1) with a double Copestake, Moore Crampton & Co., London type 15 underprint.
Note. The catalogue numbering is my own as this underprint variety is currently unlisted by Stanley Gibbons.
Normal "double underprints" show a complete double strike of the underprint just off true, giving a blurred effect. The above example however shows a partial second overprint offset vertically by quite some distance. In the above example the partial underprint is offset vertically by almost exactly half the stamp such that the "Copestake" appears across the centre of the stamp under the complete "Moore". The last line of the partial underprint (the "London.") wraps round to the top of the stamp, appearing just below the complete "Copestake".