The ad suggests that this is the first 12-string that Gibson ever made. I don't know if that's true. The story that Dave told interviewers is that when he got this guitar, Gibson had set it up so that each string was equidistant from the others. He said he had to take it to a luthier (Harmon Satterlee in San Francisco) to have the bridge, nut and neck changed so it could be strung as a 12-string is supposed to be strung.
It seems a little odd that this guitar is being sold at auction and not through a vintage-instrument dealer. I believe the banjos that he used with the Kingston Trio were sold by Mandolin Bros. and Caruso Music and both commanded a pretty hefty sale price.
I also wonder if the opening bid and anticipated sale price are a little optimistic. The refinishing from sunburst to black long after Dave left the Trio may hurt its value.
Since I don't have an extra $10G laying around collecting dust, I'm going to sit out this one out.
There's probably someone with deep pockets who'll fork over a load of cash for it. It's one of a kind, for sure. If Dave Guard had it refinished, it may add to its collectable value as a unique item. Unfortunately, if a "collector" (non-musician) gets it, it will probably end up in a vault and not get played.
I wonder about the monetary value of items after the last people who were part of an era have passed away. Will some of the things that get top prices now, get anywhere near the money decades after the avid collectors are gone? How much will a Beatles album or poster fetch a hundred years from now?
I'm curious about the three screws on the truss rod cover. I know this may have been a special order, and I also know that it's thought to be a 1960 model. That said, I've never seen a Gibson 12 string guitar with a three screw truss rod cover. That's typically an Asian feature.
Also, with an estimate of $20,000 they may have it for a while. I own a 1965 Gibson 12 string guitar and I like it very much but it's not worth $20K. Also, you would have to think about just how much of an increase in value would come with the claimed provenance.
Furthermore, the refinished top will cut the value dramatically on an instrument such as this.
The other thing is that this instrument isn't really associated with the Kingston Trio. A 12-string wasn't used on any of their hits before Dave left in 1961. I think he may have played it on a half-dozen album cuts.
That's good evidence that he did own and play the 12 string. It's also possible that the truss rod cover could be a replacement since it wasn't unusual to have the screw hole nearest the nut strip out. AFAIK nowadays, Gibson only uses three screw versions on Asan-built instruments such as their Epiphone line.
Regardless of who played which instrument, the Kingston Trio was certainly a wonderful group. I'm sure that they also helped to sell a lot of guitars and banjos in that era as well.