An old mannheim rule, sorta like the Höltgebaum & Heinicke one, only probably older (this one lists the manufacturer as "A. W. Faber, DRGM") and with some other really nifty features: the pointer on the cursor is a memory aid for the decimal place; multiply by 100, move the pointer up two; divide by 10, move it down one. Also, in the well where the slide sits, there's a CM scale; this way, you can pull out the slide to measure things longer than the rule alone. Those nutty deutschlanders. The back of the rule has the name "Spohr" burned into it. Herr (Frau?) Spohr wasn't just a mean hand with a woodburner, either: there's a nice, very old-style, very teutonic, "W. Spohr" calligraphed on the cardboard case.
You know, when you're staring at that GRE logic problem, chewing on your Faber #2, you really don't think about the fact that they also made awfully nice slide rules.