Every S.D. Myres holster I have owned, own or have seen, has had S.D. Myres stamped on it, usually on the back of the belt loop, and sometimes on the back of the holster near the bottom.
There were many custom holster makers in the past and many did fine work, although few got to be a "name" holster maker.
This is one that I picked up for my 24-3.