If that cylinder was not shown in the sales listing or declared in the text you have every right to not only return it for full refund but refund including postage BOTH WAYS. This is not a case of satisfaction return privilege, it's a case of outright fraud. That being said, how is the timing now? Does each chamber lock up tight even on slow single action cocking? If so, it's already been repaired. Either way the gun is not ruined, just seriously marred and not worth a premium price! The dinged recesses for the cartridge rims are simple to fix and I've seen them function as is but I've removed dings like that. See if cartridges will chamber flush.
If you otherwise like the gun as a shooter, ask for a price adjustment. Large adjustment if still out of time, smaller if already repaired and in good time. The gun may noy have been otherwise abused, just operated by an idiot.
But if you send it back obtain agreement on shipping reimbursement before shipping it. If on an auction site and you don't get agreement, make a fraud complaint to the auction siteholder to get cooperation from the seller. If the seller knows he's going to be paying for shipping costs refund, he'll be much more agreeable to a good price adjustment!