You can date glass negatives, 1800s versus 1900s, by examining the glass. The glass usually differs in thickness, cut and glass quality. So I think someone could examine the negatives and tell you if they're from the 1800s.
Duly note that they quit making glass negatives and photographic slides in 1920s-30s (replacing with plastic film), so all glass negatives are antique-- the question here is 'how antique.'
I've never been particularly fond of the Vermont find cabinet cards and displays, but they sell for good money even when clearly advertised as being from the early 1900s. I've never seen one of the Vermont find glass negatives, so have no opinion on them other than others have auctioned them as original.
In case anyone's interested, I wrote a brief article giving an overview of the various Old Judge proofs and displays--
here