I am not sure if he used the Martin on the studio track, as later live performances of “Blacksmith’s Prayer” and the song’s video show Seth playing an Irish bouzouki. In fact, whether he is playing the tenor or the Irish bouzouki, Seth tunes both instruments to the modal bouzouki tuning of G-D-A-D.
However, you will notice that it appears higher in pitch than either instrument’s typical open string range. Sounding slightly lower than a mandolin, this was accomplished by Seth using a capo on both instruments at the ninth fret. In essence, the “Blacksmith Prayer’s” tuning became E-B-F#-E.
This particular cut was captured live at St. Pancras International Railway Station in London in 2011 and is part of The Station Sessions series of recordings. It gives the full effect of Seth and his Martin tenor guitar as well as his great stage presence.