I have two very similar rods one a bit older and one a bit newer. Both Battenkills and both 6 foot 6 inchers. A lot of folks say 5wt. I'll agree with most modern fly lines, I really like the RIO gold and the Wulff TTs on them but while I like the Cortland Sylk lines I think the 6wt would be better suited, especially if you aren't making distance casts. I'd agree with the value being around $600 give or take.
Either way you have a sweet rod. Mine were given to me by my father in law under the condition that I fish them. I don't fish them all the time but they certainly deserve to see the light of day and feel a fish on the end. I have caught plenty of tiny brookies, some good sized wild bows and browns, and even a hog bow out of a DH stream. I was afraid that hog was going to snap the rod, but it turned out to be a testament on how strong bamboo rods are. At any rate I suggest you fish yours on occasion too. I am sure Grandpaw would approve!
If you think it needs any repairs I hear Orvis is happy to do them.