I'm a bit confused. By express sight, do you mean a shallow V style like on the Boddingtons? I have never seen any other style than the standard 1/4 rib with the folding rear.
Those sights aren't factory.
When that #1 was built (the post says 1997), Ruger had never offered express sights on the #1. In fact, I believe the Boddingtons were the earliest to be offered with Express sights.
Chet15