I also think that a slide rule is a versatile and useful adjunct to the calculator!
Here is what I found for myself, after giving my former, somewhat simpler pocket model to a co-worker, as she was very eager to aquire one.
THIS ONE will not leave my hands, that is sure. It is marked with both the Siemens & Halske (S with H) and the Siemens-Schuckert (S with S) signs, which is very unusual. It is therefore a Siemens company issue from the mid-60s before the unified Siemens AG was founded, as the constituent companies did not work together that closely for most of the time before this. So besides being a extended-scale pocket slide rule, it is a nice piece of Siemens and German Electrotechnical history.