Some years ago. 23? Jack and Paul appeared in an pretty much unannounced show at a show at a small club in Portland, Maine.
Luckily I was on their email list. So, there were like 20 people there at most. Put into a small side room.
I stood about 10 feet away and watched Jack playing said Gibson Les Paul bass. The hollowbody you folks are referring to.
After that amazing experience I almost bought one on sale down in Massachusetts offered at $1600, as I recall. But money was tight then.
Subsequently I've toyed with the urge to buy one when I've seen them offered. But never felt obliged to spend the money on a larger form bass.
Most or even all I have seen were stamped as "seconds", usually as a result of some finish blemish.
I've played 2 of the original Gibson specimens and several of the Casady-spec'd Epiphones. Based on my experiences, the Epiphones are generally preferable from a player's perspective. I say generally because one of them was admittedly a lemon.
There's a funny story about the first time I tried one of the Gibsons. it was in Frankfurt, Germany and I found myself at the top of a high-rise in the business district, standing in an office with walls lined in at least one of every Gibson bass model ever produced up until that point... That day I got to A/B the Casady and the vintage Gibson counterpart.
My Dearmond Starfire had actually come to me in a nice Gibson gig bag, that I concluded had to have been made for an EB-2 bass, since it fit my Starfire perfectly. Once I got a hard case for the bass, I posted the Gibson bag for sale on ebay. Incidentally, a collector in Frankfurt bought it. I was flying to Germany to visit family (in the Frankfurt area) a month or two after the sale, so I offered to bring it right to him to avoid shipping. He was nice enough to invite me to stop by his office and see his collection. When I mentioned my love for Jefferson Airplane and Jack Casady's influence on me as a bassist, he suggested we pull down the Gibson and the Epiphone to compare them. To me, the Casady bass was more comfortable all around and the tone was bigger and punchier. The next time I played one of the Gibsons was at a store in NYC while on tour in 2014 (Rudy's maybe?). It was the same somewhat underwhelming experience.
I know that some structural issues of the originals were addressed in the design process of the Casady. They also modified the original pickup design to come up with the Electar JCB-1 pickup. I don't recall all the specifics, but I know at least an extra magnet was added under the D and G string. Sure there's a natural mystique about rare, vintage instruments, but in this case, I think Casady and Epiphone worked together to come up with a better instrument, rather than just Epiphone trying to make a more affordable imitation of the original. Probably the same reason why Jack plays a Korean-made Epiphone on stage. Of course the Epi's potentiometers and switch aren't the greatest and the tuners and bridge can also be improved upon by swapping them out for Hipshots, but if you're looking for a bass to use regularly, my recommendation would be to go for the Casady. Of course, there's nothing wrong with going for the Gibson for the collector's value, but I would caution against expecting it to be a "better" instrument.