Welcome to the forum, AvSec!
6183 does not appear to be shown as a recorded number in what remains of Green’s records, BUT he did not always write the number down against all the guns shown in what seems to have been the Order Book for the Cheltenham shop.
If you have the original owner’s name or initials from the case or butt oval it might be possible to cross reference an unnumbered entry?
A description of your gun, bore and lock type would assist.
6182 is shown in January 1901 so that gives you an approximate date.
