You have been well informed about this bottle.
Indeed it's 1895 Clear glass cork finished quart square bottle. Before they (Jack Daniels) desided to use the square bottles they made a few test bottles. To be honest, I have never seen them full and sealed. A real beauty !!!
I know the empty ones go for aprox $280,- / $300,-
Is there "one quart" mentioned on the back side of the bottle ???
I will see if I can get a little more info.