According to Stroebel the Lyman 57 receiver sight was introduced in 1938. He further states, "The first No. 57 sights had a "clip on" tin index plate over the face of the slide. This feature had disappeared by 1950, and was replaced by a movable scale, held in place by a single screw." I have never seen the early style index plate on a 57SA.

I have a reproduction 1949 Lyman catalog (#34), and the application sheet accompanying it shows only the 56S as a receiver sight for the Model 99. The Cornell Publications website listing for the 1951-1952 Lyman catalog (#36) shows the catalog cover and the page for the Lyman 57. That page shows a Model 99 with a receiver sight on it (presumably a 57SA), but when I blow up the page it is too blurry to read.

Based on the above, I have come to the conclusion that Lyman did not introduce the SA version of the Lyman 57 for the Model 99 until 1950 or 1951. Can anyone confirm that my conclusion is correct?

Thanks.

I can't however I have seen other 57s with the "clip op" index for sale on eBay. My crude guess was that were made in the late 40s. I'm pretty sure the Redfield 70 came out before the 57, and I'm comfortable saying those sites were out by the late 30s. I'm not so sure of myself in making that statement about the 57SA.