From the pic, yeah, it looks good. Definitely worth $400.
That said, I have bought and sold many guns on gunbroker.
The problem you run into when selling guns on the auction sites is the buyer has to pick up the cost of shipping and the FFL transfer.
Without getting too detailed, unless your're an FFL, you're looking at an average of $50 for shipping and $25 for FFL transfer on their end. Plus Gunbroker gets about 5% from you when it sells. This is not a big deal on an expensive gun but on a $400 gun the buyer is looking at around $475 to get it in his hands, and he's buying it sight unseen. So... it may be harder to get that $400. Lots of good pictures help.
Try doing a search on gunbroker to see what model 15's are selling for. Click on revolvers then type 15.
If you sell it to a gun shop, they have to eat too, so your likely gonna get about $275 to $300 for it.
You can also try to advertise it locally.