That Horsley is a bit odd. The Proof Exeption certificate is dated 1988 but the proof marks are dated 1999. The proof marks are for London re-proof; now where are the old marks? Looks like a new set of barrels were made for the gun and it was re-proofed. If new barrels were made for it by anyone other than the person entitled to be called the 'maker' then it should say 'new barrels by' on the rib.
I think the presence of the exemption certificate is confusing some here. The certificate was obtained before Sotheby's sold it in 1988, but the proof marks clearly indicate that the new owner went ahead and had it reproved in London during the following year.
The proof marks are for London re-proof; now where are the old marks?
London has required the removal of the old marks from the flats (but not from the water table, for obvious reasons) for a long time now, and, to my knowledge, still does. For example, I recently examined a Holland Royal .375 Flanged Magnum built 1925 and reproved in London between 1955 and 1971 (18.5 tons, but absent the date code introduced in 1972). The old marks had been struck off, but the original "300 MAX" was still legible on one flat. I don't know when London began doing this, but it appears it was before '71.
Looks like a new set of barrels were made for the gun and it was re-proofed.
No indication of that at all. Flats struck off and the re-proof mark used is normal for a current London re-proof with original barrels. If proof is conducted with new barrels, the re-proof mark should be absent.
The marks indicate modern nitro re-proof in 1989. Only proper measurement can establish for sure, but relatively recent re-proof would seem to indicate that chances are good that it remains in proof.
![[Linked Image from i.imgur.com]](https://i.imgur.com/qclHjMQ.jpg)
