There is one other SBH grip frame with round guard the same size as the sq back trigger guard dragoon grip frame. The SBH Hunter model and is only made in stainless steel, but they can be blued.
Here's one on my SBH standard model:
And here's another on a 45 Vaquero with 5 1/2" barrel and also the extra long 5" SBH 10" barrel ejector rod & housing:
Wow, nice. I have small hands, but just can't get a comfortable grip on the single action grip. I have a 45 Colt on the large frame and a 44 sp. on medium frame and the 44 sp. has the bisley grip. Triker