I have an old Harmony Monterey that belonged to my father and has been hanging on the wall strung for 16 years. The neck has always been bowed as far as I can remember so I happened to pull it down this morning to checked it and the glue on the back could be heard by putting pressure on the neck. I unstrung it, and the spline and back came off without any issue in tact. All of the glue is brittle, but I now have easy access to it, and it needs a truss added on the back to keep the neck from bowing (the body is not that strong).
 
   So, then I start thinking what to do... it is really more of a keepsake, but if I make it playable would I ever play it? Probably not, since I would need to refret it, and if I did that then I would want to play it. But it is not a great guitar and the sound acoustically is not great either. I went looking to find out what year it might be and a picture stuck out because of the knobs which ended up being from this site http://www.chicagofretworks.com/2009/01/07/vintage-harmony-archtop-custom-pickup-mod/ Of course, my first reaction was this would make it playable, but resonance issues on this would be a bear (it is not reinforced properly internally, at least "now").
 
   It is probably best to leave it as a heirloom; I remember my dad saying how proud he was when he finally saved up the $12 to buy it. But seeing that someone put a pickup in one was interesting.
 
  

My first electric was a brand new 1963 Harmony Stratotone Mercury (not my photo) that looked exactly as shown.
 
Through the years and when I was younger I made changes such as adding HB's..painted it and...just a kid messing up and having fun. ( I was playing gold top LP's and such by '67-68 best I recall)
 
Not long ago I decided to gather up all the pieces and go for it.
Installed new body binding, wound 2 mini HB's, refretted, had the tailpiece re-chromed, make a Wenge headplate (after filling all the holes-then redrilling correct ones for new machines), Wenge pickguard and truss cover, new electroinics and painted it black with a gold top (like LP).
Reconditioned the fretboard and radiused to 12".
(at work and can't get picture but there is one on the forum somewhere)
 
I'm very glad I did. It plays great- doesn't sound all that good and has to much neck angle which I might correct some day but still...I enjoyed doing it and sure enjoy having my first electric guitar playable.
 
So I say go for it and see how things work out.

Well I guess if you were hoping this place would help you determine it- after 35 views
I'd say you may just want to flip a coin.

Damn... that is temptation galore there...
 
Honestly, this body is not solid... and the only 2 (flimsy) trusses in it are glued to the face (you can see them in the routing job from the OP actually). However... the back is off, and I could actually put a solid beam in the body and essentially turn it into a thru-body neck (but even the neck had no trussrod in it). That would also alleviate the increased fret action when strung too.
 
I am not is a rush with this one. I actually hung it back up for now. I will have to decide if I want it for "show" or for "go."

I'd pull the fretboard. Router out for truss-rod and replace the fretboard (new).
I'd make sure the original braces were good or I'd replace them. (make all internal repairs since back is off)
Then I'd put the back, back on. The body was solid once and I'd make it solid again.
 
Why? Not because I wanted to improve it. It would be fun because the guitar has sentimental value and I'd want to make it so it could be played. Same reasons I restored mine. It wasn't so much about how it would or could sound. It was the trip for something that meant something to me. Plus the experience is always a biggy.
Just my view...not trying to persuade you.

I have never installed a truss-rod, so would have to look that one up. I have put bass frets in every guitar I ever refretted, so I am thinking that may help with the fret action, but stiffening the neck/body would add even more to that. The glue is incredibly brittle, yet I do not see any movement in the neck at all; so that part  is baffling me (it is only glued on). If I wanted to, I could knock all of the glued parts apart, I think, except for that. The wood is so damn thin I feel like I am working with balsa wood (I have never torn an acoustic apart like this). I am actually surprised it didn't collapse under the stress of the strings.
 
If I tore it down that far, I would probably refinish it too... but then I wonder about the "playablilty" of it. I remember playing it years ago - the action wasn't great, and acoustically it was sad because of the "f-hole" design. An electric pickup would change that, but then I am wondering if I would actually play it. I definitely need to find info on the truss-rod, since that one is new... but I an not sure how to unglue the neck. Have you ever broken that joint?
 

No. Very little restoration work on acoustics but wood is wood. However I do currently have an Ibanez acoustic/w piezo in my shop that I'm repairing.
 
Technical work takes special tools as you know.
Removing necks and fretboards is applying heat.
An iron can be used to remove a fretboard (once the frets are removed) and steam can
be injected into neck joints. ( I do use steam to bend wood)
Naturally there are issues with moisture so best to know what the rules to the game are before playing.
 
Installing a truss-rod is not rocket science but it does need to be done with precision. Many youtube
videos on all of these areas of building/repair.
 
I assumed from your OP that you were experienced with building/repair.
I do think that if the guitar has a lot of sentimental value the best move to make is take it to a luthier
and get his/her take on exactly what it is and what it could be. That shouldn't cost anything but time.
It will help you decide best course of action, if any.
 
 
 
 

I ended up just securing the internals of this by chipping away all of the glue and running a bead of gorilla glue along all of the seams internally. Finally I notched both end pieces and put a 1.5"x3" truss down the back of it, so it is solid as a rock and will remain that way. The only markings inside the body was an ink stamp of "S 48" on the inside of the back (assuming that is a date stamp).
 
After I touched up some of the distressed points on the body, I put on 2 coats of Tru Oil which changed the appearance dramatically. Then as I bounced around wondering what to do, I assembled it and put on a set of electric 10s just to check it out. It has a lot of things that would need to be done to make it playable (frets and better bridge specifically) and I really do not like how thick the neck is (too thick for my tastes), so right now it is hung back where it came from. It is really more an antique for show rather than playing, but it does sound nicer than it did and definitely will not be coming undone in my lifetime.
 
Thank you very much for the feedback! I wanted to evaluate it reassembled first, but I know this would never be played much since I have similar guitars I rarely touch as it is, so best to keep it as I remembered it growing up.