Don't chance losing that one by negotiating, grab it now! It would sell for at least 3 times that amount here in the US! You're not likely to find another like that for sale in a lifetime.
When or if you get it please post the serial # and we can tell you much more about it. It's likely a British service revolver made by S&W for them for the 1st WW. Chambered for the .455 mark I and II cartridges.
Well, there are a few ways of purchasing a firearm and negotiating. If this revolver is available from a private seller or at a gun shop in person, and it's one on one with the seller, it can't hurt to offer less. Most folks are okay with dickering,
especially in Europe. The worst answer is usually "non negotiable!"
If on an internet site, such as this revolver seems to be, IF the seller posts a phone number and he picks up the phone, you can discuss briefly and negotiate. Same with text messaging. Also, emailing and receiving a response quickly, within a few minutes. Of course, there's always a risk that someone will swoop out of nowhere and snag it. The way around this is to post "will take it pending discussion", which most honorable sellers will honor, and then bring up the blemishes in the finish, ask if the seller thinks it might be refinished or not, and the blemishes might get you a sale price of €1000, but you're prepared to pay €1100 anyways, as you know it's not refinished and the imperfections are inconsequential.
Given the time that has elapsed since the OP posted his thread, he should be responding by now that he got it, or, by now, that, unfortunately, someone else got it. Unless Triple Lock revolvers are just that unpopular in Italy, I can't see this revolver still being for sale, now nearly 24 hours later.
So, then, what is the fair market revolver of the .455 Webley I purchased earlier this year for $1232 plus shipping and FFL fees, which means it cost me roughly $1300 in total? I value it at under $2000 being in .455 Webley and not rechambered for .45 Colt. Mine is clearly nicer than the OPs, and your claim suggests that the OPs revolver is worth greater than $3000 in the States, and mine would presumably be worth even more. For that kind of money, I would expect a similar condition standard configuration Triple Lock revolver in .44 Special, a .44 S & W Special revolver in the Target Model configuration in a bit lesser condition, or Triple Lock revolvers in similar or lesser condition with barrel lengths other than 6 1/2". Probably I am referring to the 5" barrel length, as a 4" barrel would be unlikely in this barrel length. Having said that, within the last year, I DID purchase a standard frame nickel Triple Lock revolver with a 4" barrel WITH factory letter and with decent condition and I paid nowhere near $3000 for it. And only about 125 or so Triple Lock revolvers were purchased in this configuration.
So far overlooked in this discussion is the following: Has this revolver been rechambered to .45 Colt? In which case given this revolver is in Italy, it's still likely worth close to €1100. The easiest way to know if this happened is to see if the revolver chambers a loaded .45 Colt round. If it easily chambers, it's been converted to .45 Colt. If it gets stuck 2/3 of the way in—Congratulations! The revolver remains chambered in .455 Webley. If the availability of a .45 Colt round is impossible, please post good photographs of the chambers, the inside of the recoil shield, and the face of the cylinder and we can assess to see if original or reconfigured. Please post those photographs, irrespective if you think the chambering remains in .455 Webley or not, as we can all learn from good photographs.