I've got a mint Model 10 with a two inch pinned barrel and a round butt frame. Great carry piece. I had one with a 2" pinned barrel and a square butt frame, too, but sold it last month. Already regret the sale. It was an old one (late pre-10 M&P), and in very sweet condition, having almost 100% of its original blue, and not a speck of rust nor a scratch on it.

Once they started putting the round butt frames on these, the square butt frame snubbies stopped being popular and thus production of them slowed down or stopped, so you don't see a lot of them with square butt frames after a certain date.

Here's mine: