Agree with the above, but just a minor correction on values. The only vintage Martin in excellent condition that can command the prices as mentioned above is a pre-war D-45, of which only 91 were ever made. Elderly recently had one which went for $140,000.00 and it wasn't mint, and had a few repaired cracks.

A pre-war D-28 in excellent all-original condition is in the 40K range, and a D-18 in similar condition would command between 18 and 20K. Old worn, pre-war bones would be in the 18-25K range...with D-18's of similar age and shape to be in the range of 12-18K.