Well the OP has not been around since June 6 months ago, so this is well on its way to being a zombie thread. I will add this as a parting comment tho.

Jeffery is said to have used "serial number blocks" so tough to get a pure chronological guess on production date. That said, understand that Jeffery did not allocate individual serial number ranges to specific models or types of guns/rifles, just whatever was next, be it rook rifle, shotgun, single, or double rifle got the next sequential serial number.

As noted above, my Jeffery .577BPE is serial number 2457 and is Feb 1896 from the daybooks. I have an extraneous daybook page for low 4700 series numbers that is circa Summer 1896.

An interesting side note: the rifles & guns listed on the (admittedly few) daybook pages that I have from 1896 were all made by Ellis for Jeffery.

Such a shame that the extant Jeffery daybooks are so closely held & difficult to access.
- Mike