I have a CF Mountain guitar that I bought for £50 second hand in Bristol in the early '80s. Mine is a model W150 with a label in the sound hole and a logo on the headstock that looks very like a Martin logo. It seems to be a copy of a D28, and plays pretty well. It has a few scuffs but is generally very good. Unfortunately I can't find a serial number. It appears to be a spruce top, (possibly solid - definately thin) with laminated mahogany sides and back, plus mahogany neck. No idea of value, but certainly plays and SOUNDS better than anything in the shops at @ £100 today.