Re: [Slightly O.T.]: Unfinished Wood Instruments
The purpose of the finish is to protect the wood exposed to normal every day life, much like a table or chair. If left unfinished it can cause many issues and the wood will develop many issues over time that may affect its life. Would finish prevent the issue you see with the back crack? Possibly, but cracks develop in wood due to rapid alterations in humidity. Finish may have helped, but may not have prevented this kind of damage. On the other hand, the finish does help retard the speed humidity changes may affect an instrument.
Your guitar should have improved in tone over the years. That is a fairly common experience. Depending upon the kind of finish you would have applied, the tone may or may not have improved to such a degree. One of the reasons nitro cellulose is used for a finish on an instrument is because it will allow the instrument to improve over time as the wood ages and progresses. Some heavy poly finishes are like dipping the instrument in plastic and not much improvement is likely to happen.
You are fortunate not to have more damage to the wood without finish. It certainly can be refinished and its look and integrity restored. Needless to say, the back crack certainly needs attention. Overall you are very fortunate your guitar has not self destructed, but we restore lots of old instruments where the finish has disappeared and the instrument has survived. It may need lots of work, but it has survived.
Pictures offer an interesting view to an instrument, but don't tell a very complete story. From the photos it appears there may be some finish left on the instrument producing the gloss seen in the photo. However, a flash may cause that appearance as well.
Have a Great Day!