This is an easy but also difficult subject. I have bought and sold on the site often. You have to make sure the people you buying from in well reviewed and if they have a bad review like ebay it could be a hater or a misunderstanding or just right.
If your worried check for a return policy as some do have them. Ask them as some are willing and some aren't to take more or even more specific photos of certain areas. Yes, photo shop can be used but again there is where the credibility and return policy come into play. If they have a retail location or if they are just a private seller can be good and bad. If its a retailer they usually have a phone that you can call but not all if you have questions.
Trust your gut. If it doesn't feel right don't get it. Do a search on GunBroker for your gun and see the different options. Keep in mind there are new listings daily and you can place things on you watch list where if you get outbid you can get a email. Stay away from GunsAmerica and best of luck.
I've never bought from an individual on gunbroker. I only buy from actual dealers and try to stay away from the pawn shop guys. Know I've missed out on what was proably a good buy and good firearm but still unless they have over 100 firearm sales I pass. So far no problems.
If I can't find what I want at a good price from a Local Shop or from a local private sale then I go with someone who has a good rep like Mark at Summit or other online place/person with a good rep.
Also, if it's a private sale online I'd see if I could get them to give you a trial period so you could return the gun if you weren't happy with the fit/finish, ect. Not everyone is willing to do that but if what they're selling is as good as they say then they should be willing to let you look at it when you get it and return it if you're not happy, otherwise I'd be kind of leary about buying from them.
I have bought and sold several guns on gunbroker. I have never been unhappy with the guns bought. Although, usually I have handled the model I want at a local gun shop or a gun show before I bid on one online.
You will also notice that many of the Smiths on Gunbroker will have a pic that hides the lock......either the right side, or tilted in such a way that it's not very noticeable.
Those guys are well aware that the lock means that half, or better, of the potential buyers just don't want the lock.
For myself, I've avoided getting one with the lock alltogether..... I know that Smith is still producing some fine revolvers.....but, the lock is just a reminder of the shenanigans that Smith pulled for political favor in the Clinton years.