It's a double barrel 12 ga. It has a dolls head and two locking bars in the lower receiver. I believe it's called a side lock, with external hammers and double triggers. The barrels are removable. The breech is opened via a lever between the hammers in the conventional manner. It is finely engraved, and checkered, with a horn butt plate. On the right side plate it has "Hy Wynian" engraved, not stamped. On the rib above the barrels is engraved "London, Fine Damascus". Under the fore end are British proof marks; two for each barrel. Along with the proof marks the left barrel is marked "Not for Ball". A few years ago I came across a book of proof marks and learned that the British only used the marking "Not for Ball" between 1887 and 1899, so I have some idea of it's age.
Since one barrel is choked and the other not, I'm guessing it's an upland game gun.
I'm not interested in shooting it, even with black powder, but would be thankful for any further history about "Hy Wynian" anyone could offer. I'm wondering what it would be worth, though I'm not planning to sell it. Thanks to anyone who can shed some light.