Anyone know what joint is inside this beast?
Dovetail potted in lots of hide glue.
Yes, but the important question is whose signature is that on the top?
I did the same thing. I wonder if...
OK. Better make sure that you don't refinish that top!
I took one of these on years ago. While it was a regular dovetail, it required an extraordinary amount of steam to release. I also had the problem of the binding coming off at the side dot markers when loosening the fingerboard over the body. I can see in your pictures that the binding has some cracks propagating from the side dots on the 15th and 17th frets, so you may end up with the same problem. Good luck!
Use the cartridge heater/heatstick . and water. there is a ton of hide glue like frank said. it needs heat and moisture to let go. like 30-60 minutes. the steam is too inefficient and causes finish problem. they are faced glued too and finished over so make sure that joint is free as well as the dovetail