Indians For Guns

We all know that when we disassembl a pistol we remove a Barrel in Many of the models like Asani, Colt Beretta, Remingaton 51 etc.
but what with Revolver. Todau I surfing a Net, I found one of the site usedguns.com.eu. On that site I found a Smith & Wesson Model 686 357 Revolver with extra barrel( with screws).I post the picture on that picture the web site add are appeared. According to my knowledge Revolver had a fixed barrel. Is t possible, if yes than can we also remove ours Ofb Revolver.

Barrel on IOF revolver ( webly type ) can't be changed cos it is one piece machined off with front half part togather

Yes it can be done, but there may not be a lot of good reasons to do so.