I said to myself, try once more to find markings on the spine. My little 40x still showed nothing, and my 100x had its clear plastic end too far from the spine to pick up the details. I still had some CLR in a jar, so I went at it again. @!*% if I didn't see a beautiful "S", then others still too faint to identify came into view. The first two photos show the "S" with my pen mark, just to make it easier to start taking the photos.
I can't tell if I have the photos right-side up or upside down, but think they're right. The "S" is closer to the muzzle, and the third photo is closer to the breech.
Come tomorrow morning, I'll go outside and see if my Kodak Pixpro can do better resolution-wise than my wife's iPhone. If anyone has any ideas at all on what the letters are, please reply. Looks to my 40x eye that several letters have horizontal top and bottom markings as accents(?) to the individual letters.
Is there any type of pen or substance I can apply to the area to better expose the parts of the letters that still have some definition/impression? I tried using a black felt pen but was of no benefit after wiping with my finger.