I'm not going to claim to be a DW expert, but I love them and have done a bit of research on them over the years. The Model 9 is chambered in 38 Spc, not 357. So if it is a 357, then it's a model 15, not 9. Dan Wesson didn't put the model numbers on their guns, so it can be a bit tricky to tell sometimes. The model 9 and 15 will look pretty much identical, even the cylinders are the same length, however a 357 cartridge will not fit into a model 9 cylinder because it is reamed differently.
Since the barrels can be interchanged, it could have a 357 shroud on a model 9 frame. Did the barrel say 357 or 38 spcl on it?
The easy way to tell if it's a 9 is to try dropping in a 357 cartridge. If it fits, it's a 15, if it doesn't, it's a 9.
If it truly is a model 9, I'd jump all over it, they are quite rare.
Even if it's a 15, I'd probably still jump on it if the price is reasonable and it's in good shape. They are fantastic revolvers and are getting harder and harder to find.
