9,5D Roper Toe. 10” Shaft Last: Size not specified
After owning 6 different boots made on Rios of Mercedes Lasts I have dialed in my size with them to 9.5D generally speaking. There’s variations though. I have a feral pig skin boot from Rios in 10D that fits like a 9.5 D and a Mad Cat Goat Boot from Rios in 10D that fits like a 10D sneaker size. It depends on the boot but generally with Rios of Mercedes a 9.5D does the trick for me.