I agree with Ky Jon. That choke business was a question mark for me. The closest Reilly this gun comes to in my database is 17392 - a 16 gauge - one of Terry's (see below)
--(note false percussion cap fences)
--(note left-hand side-lever)
--(note Birmingham BP proofs...this gun is odd).
I date 17392 to early 1872. Choke boring as we know it didn't begin until mid 1875. With Birmingham BP original proofs and with IC chokes...17392 had to have been rebarreled by Reilly after choke boring began in earnest. Either that or there was something going on with honing the barrel later that could create an IC choke, something I don't know about.
This is one of the reasons I've asked for the SN on Steve's 12 gauge. I'd like to get a look at the barrel flats as well. There should be no "not for ball" if it too is pre 1875 as I suspect. Steve got back to me...said he'd have his secretary send the SN - he's traveling.
================================================================
17392http://www.amoskeagauction.com/110/132.phpserial #17392, 16 ga., 28" barrels with bright excellent bores
choked improved cylinder in each. This shotgun shows period
Birmingham black powder proofs with later
London Nitro proofs and modern "70MM, 900 BAR" proofs. The barrels are generally over .030 everywhere except for one spot in one barrel that gets to .027". The action and locks show near full coverage scroll engraving with no makers name appearing on the action or locks. The barrel rib is engraved "E.M. REILLY & CO. NEW OXFORD ST. LONDON" and retains 95% beautifully restored brown finish with strong damascus pattern their entire lengths. The action and locks retain an even grayish patina with rebounding hammers and crisp locks. The checkered straight grip walnut buttstock and forend rate very good plus with a good deal of original finish, perhaps some added light oil and a beautiful toe and heel buttplate with checkered center panel. The shotgun locks up tight and features a 13 3/4" pull with drops of 1 1/2" and 2 1/2". A nice tight sidelever Reilly small bore double that seems like she's ready to go. (17147-143) {C&R} [Terry Buffum Collection] (1500/2500) SOLD FOR $2,185.00