M-30 value
It's hard to put a price on this model, since there is no market history to speak of--in 20-plus years of looking, I've seen exactly one, a '59 in good condition. I paid something like $200 for it more than 15 years ago. I suspect that it would bring more than that today, but I wouldn't know where to start. They're very rare, and mine at least is quite nice, but (in a rational world) not necessarily all that valuable, since similar instruments can be had for well under a grand (the Martin 17 series). I'd also think that the (rather inflated) price of an old M-20 would suggest a ceiling value, since Nick Drake never played a -30.