This is a 12 (double 6) string guitar. Mark used the guitar on Angel of mercy during the On location tour in 1981. Click here and here and here for some pictures of that early period. On 20th June 1986, Mark used the guitar again at the Prince's Trust Rock Gala on the song Sailing by Rod Stewart.

This is Mark's other 12 (double 6) string guitar. Richard Bennett used it in March 2009 on the studio version of Cleaning my gun and used it live for that song aswell on tour; Get lucky tour (2010), European tour with Bob Dylan (2011), US & Canadian tour with Bob Dylan (2012) and the Privateering tour (2013).
 

This picture is taken by Guy Fletcher in British Grove Studios in May 2011. The White Bison is indicated by the red arrow.
Click here for a better picture of a similar guitar.