Martin’s music has always had a leaning to American styles, banjo and slide guitar amongst them, and he usually plays guitars made by Roger’s friend Stefan Sobell. This time Martin asked Roger to make him a resonator with just a little less “edge” to the usual sound and provided metal parts which Roger built into a suspended tone chamber within a more or less standard acoustic guitar. The back and sides are Cocobolo, a very hard, fine timber that provides weight and sustain behind the fine Englemann Spruce top, the overall effect being to add more of the low “partials” to the otherwise metallic tone. This guitar can be heard on Martins album “Prodigal Son” The strange soundhole is either S for Simpson or F for Fylde. Or both.