Nestler No. 20 "Kiel", 10" Mannheim
This slide rule has three lines on the cursor, "kW", "q", and "PS d". I haven't dated this rule yet, but the screws in the ends are a hint that it's pre-WW II.
There is a name engraved in the bottom of the "gutter" underneath the slide - "Hermann Schwerdfeger, Wesermünde - G." I had originally thought this was the owner, but I've seen this same name on other Neslter No. 20s on the web - perhaps it was a dealer or something.
I don't know what "Kiel" means, but "keil" means "wedge" in German.
Nestler No. 40 "Hutton's Commercial Slide Rule", 10" Special Rule
This is a very interesting slide rule, as it has special gauge marks for converting one form of currency to another - back when the Gold Standard ruled and exchange rates were fixed! It also has special gauge marks for inches and feet, kilograms and pounds, etc. Best of all, it has an I scale for calculating interest.
I also just bought a Nestler No. 24, but I don't have pictures of it yet. It's 23 inches long!
© 2003 W. E. Johns