My approach would be to make a new bridge with a slightly larger footprint to cover the gaps as I reckon a touch up round the edges would look noticeable. I can't make out the finish crack on the seam from your picture but if it's faint it can be touched up with a fine sable hair artists paint brush and then buffed down.

My tuppence worth.

Bill S.

what is the best approach to this repair to maximize vintage value?

Not to be mean, but the best approach is probably to pay someone who specializes in vintage restoration work to do it, assuming you do not already consider yourself an expert.

If you want to do it, definately do the touchup while the bridge is off. It is a tricky job, because you have a line going straight accross the grain and it will be difficult to match the color well enough that it won't stick out. Fortunately, the repair will be close to the bridge and may be mostly hidden by the shadow cast by the bridge and obscured by the strings over it.

I would find some scrap spruce that was close to the color of the top, make up a few samples of tinted lacquer (i usually use the colortone stains from stewmac) and brush some tests on the scrap. Once a good blend is found i would brush the lacquer on the guitar, building up layers over several days until the color looked good and it could be leveled out. Then polish it up with micro mesh or your prefered method. After the touchup is done i would carefully score and scrape away any finish that was left under the bridge outline.

Also read up on touchup over at FRETS.com, there is a bunch of useful stuff there.

If the top seam is actually sound, i might just leave it be, it is hard to tell in the photo but it may just be the finish checking as a natural part of the instrument aging.