I'm not familiar with the 10-15, I have two 10-14's and I thought they were the last Model 10.



5" round butt 10's do exist, technically this is an M&P made in 1956 right before the change to model numbers but I still believe rb 5" 10's were made after 1957.

This one is marked E. Cleveland Police on the blackstrap. It's one of my favorites, just need some original diamond Magnas for it