Hi Gary, Just browsing through an old Weller & Dufty catalogue, dated 12th December 1966.
Came across this item:

"A high quality double barrelled underlever .450 blackpowder rifle, by E>M> Reilly& Co. Serial No.21300. Damascus barrels, with matted rib, bolted back action locks beautifully engraved with fine scrolls, chequered fore-end, and pistol grip, nicely figured stock with cheekpiece, sling eyes, hammers repaired, very good condition and working order, with some original finish. Barrels 26".
Do you have any knowledge of it? I have hundreds oif these old catalogues, and I aim to try to go through a few each day. I will list any Reilys I find, plus any English pinfires. Dave