The checkering looks re-cut..not necessarily a bad thing. Just something to note.
I'd guess from the pics that the bbls are re-blued. They look really great, maybe too good for the rest of the gun. The normally polished up breech end & lug
a bit too bright and new polish looking.
Again, just an observation.
The proof info from the bbl flats would be a must to determine if the 2 3/4" chambers are original.
'In Proof' seems to be so important on Brit guns.
You can do most anything to anyone elses guns and as long as it's done safely, there isn't much said.
Cyl/Cyl chokes certainly possible as orig.
But is that something you would necessarily like to have.
Here's a 12ga Thomas Wild on Hollowell's site. It's redone and a PW grip stock.
The excellent pics show the crossbolt on the left side of the breech and how they hid the round bolt in the engraving scroll work which is much the same as on
this 20ga,
http://www.hallowellco.com/thomas_wild%2012ga.html