Just a little comment regarding the SP101 rear sight on the .22 version. 10 rears ago, I went on a hunt for a S&W 63. I couldn't find one. Those I found were too expensive. In a small gun shop in rural Missouri, I found two SP101 .22s with a four inch barrel. One was new with box and all accessories. The other was used without a box. I was a bit put off by the appearance of the rear sight, but as I hefted the revolver, the sight picture was as big and clear as any S&W sight picture I've viewed.
Long story short....in my cheapness....I bought.... you guessed it, the used one. I took it out to shoot it and found that it put a cylinder full of any .22 ammo I put into the cylinder into one ragged hole at 15 yards and into 2 inches at 25 yards off sandbags. Double action on 10 yard tin cans made them bounce everytime.
I went to visit my sister and my brother in law and I went to the range. He took his new Tarus .22 stainless kit gun. The Ruger outshot his, when his would go off. The Tarus had a really heavy trigger. His looked like a S&W 63 clone.
Eureka!! I guess William B. Ruger knew what he was doing. He made an adjustable rear sight that instead of being a part of a dellicate assembly was burried into the topstrap for protection while maintaining a very useable level of accuracy.
After a month of realizing that I should have bought both revolvers, I ran back out to that rural gunshop to find that the other one was gone. Those were the only SP101 .22s I have ever seen in my life. I regret not buying both. Glad I bought at least one of them. I'll take 5 more of them if I can find them for other family members. They covet mine, will work for defense if need be and for every day economical enjoyment.
Again...Bill Ruger knew what he was doing.
Bill