Identify Double Box End

[altersaddle]

This came in a small tool box full of assorted tools:



Near as I can tell it is a New Britain NDF-206. 25/32 and 3/4 ends.



Does anyone know what the "S" forging mark means?

How can I determine the finish? It's not shiny chrome.

 

[bonneyman]

Late 40's and on smooth shank style New Britain.

http://home.comcast.net/~alloy-artifacts/newbritain-nonebetter.html#newbritain