Well, the seller knows enough about it to have used an accurate serial number chart!
Buffet was a licensee for A. Sax instruments, so you'd be getting a horn that should be almost identical to an A. Sax instrument from the same time -- and from about 7 years after Buffet started making saxophones. 'Course it's also probable that it's high pitch or French Standard pitch.
(I've seen things that indicate that Aldophe-Edouard Sax took over saxophone manufacture from Antoine-Joseph Sax sometime between 1882 and 1894, the year of AJ Sax's death, so YMMV.)
Pricing is difficult. If it was an AJ Sax, you're talking thousands. Buffet and other Sax licensees' horns generally don't sell for much at all. It'll be interesting to watch. Hey, if I was still teaching, I'd love to have one just so I could demonstrate to my students. I wouldn't pay *that much,* though .