I have seen 10-9's, I don't think they are very common and all of them have been RHKP marked guns.

Both 10-7's and 10-9's seem to be rarer and most if not all probably all went to special orders for police contracts. By the the 4" HB had become the "standard" for S&W's M10 production and they were phasing out the taper barrels.

I've never seen a round butt for either a -7 or -9. Then again, I had never seen a RB 4" 10-8 until I bought one. You never know what's out there.