My latest acquisition: a Russian KL-1 pocket-watch style slide rule. There are different scales on each side for different calculations. One of the knobs makes the scales rotate, the other knob makes the hairline cursor rotate. Manipulate those properly and you can perform all sorts of mathematical prestidigitation, in a package easily carried in the pocket.
I acquired this one on eBay from someone in the Ukraine. It's in excellent condition, works perfectly, and came with a little round case. I added the thin foam sheeting to one side of the case to keep the rule from rattling.
Instructions for the gadget are all over the net, the originals being unintelligible to me, being in Russian, but there are decent translations, and it isn't really hard to use if you are at all able to use a slide rule. Circular slide rules are a little weird, but they work just like the regular kind, of which I own several. I guess I'm into collecting the things now, at least to a small degree.
They're nice to have if you need to do math and don't have a calculator, or your batteries have gone dead, and for some reason your computer isn't working either. So if the SHTF and all of our electronics gets fried by a big EMP, those who own and know how to use slide rules can still get the math stuff done. (Provided, of course, they know how to do the math at all, and have a reason to use it.)
I got hooked on slide rules in 6th grade, when my science teacher gave me a cheap one and a book called a TutorText -- sort of a "choose your own adventure" book for learning how to do something -- on the slide rule. (Those books are rare these days and cost like gold or gunpowder.)
If you are in an engineering trade, into electronics, or anything that might require complex math, learn to use a slipstick. You can spend any amount of money on the things, they're unbelievably collectible, but you can get a GOOD one, either full-sized or the 6" "pocket" size, for about $25 on eBay. I never bid, I only get items that have a "buy it now" button, because no one can win an actual auction unless they use a bidding program to do it for them. I don't bother, I spend the little extra to buy it outright from the beginning. It's quite possible to get a rule for a cheap price that can be resold for a much higher price elsewhere, but I'm not to that point yet. I just love the things as the historical geek gadgets they are.
There's a hatful of websites all about them, like the International Slide Rule Museum and the Oughtred Society. Most of them have a section on learning to use a slide rule, and some sell them -- but be careful of their prices. Those are collectors' prices! If you want a rule to learn on and to keep handy for just such an emergency, get one on eBay or look for them at flea markets. It doesn't have to be a fancy one like Kip Russell's K&E Log-Log Duplex Decitrig from "Have Spacesuit Will Travel" -- I own both the full-size AND the pocket versions of that rule -- it only has to be a simple "Mannheim" style rule with the A, B, C, and D scales. You can probably find one of those for around ten bucks, but I usually splurge for the fancy one with a dozen scales for just a bit more, because I think they're cool.#SlideRules #GeekGadgets #Oughtred