Aha, I found more hits when I entered "Friden STW." I don't know where I got the "55" from.
http://americanhistory.si.edu/collections/search/object/nmah...
It's fully mechanical and can do addition, subtraction, multiplication, and division. I saw one of these things work, and it was quite an experience. There's a YouTube here:
https://www.youtube.com/watch?v=qKm9eM2BuM0
And a few people have published images of the service manual.
My dad said that while the Friden was accurate, it was not portable or quick, and he usually used his slide rule, notebook, and graph paper. For a chemist, slide rule accuracy was usually sufficient.