Hello 500Nitro,

The rifle is a John Dickson double rifle in 577 caliber.

Per the original John Dickson ledger, it was originally built in 1868 with the following specifications:

"a double central fire breech-loading rifle, number 2894, gauge 12, for James Robertson, Esq., (stock dimensions) weight of barrels 5 3/4 lb., length 27 inches. Back lock, charge of powder 3 drams, stock unvarnished, spur guard."

What wonderful information!

But, it is no longer a 12-bore, it is now a .577 caliber. This is unusual. However, the Barrels are marked "577EX" and "AH7186".

As I have learned, "AH" with a number, typically references Alex Henry, and the rifling in the barrels of this rifle, is Alex Henry type. A call to Dickson and McNaughton in Scotland with a request to search the Alex Henry ledger indicated that Ledger serial numbers stopped well before the AH7186 number. But, the Ledger also contained some unregistered numbers for after-market work. And there, the number 7186 was listed. It read:

"Specifications of number 7186 - New barrels to Dickson rifle, 20-.577, 28 inch steel, nitro proved, upright sight--standing and two leaves, 1-2-300 yards, usual front sight--plate tip, 26th Nov., 1900, Kynoch solid drawn shell, 70 grs. rifleite, 650 gr. bullet, nickel coated soft nose, barrel weight 7 lbs. 10 oz. for Cap't McNeill."