When I was a student, I used a slide rule for most of calculations. And I used a 7 digit (?) Logarithmic table if I wanted better accuracy.   Electronic calculators were developed in early 1970s, and, especially after introduction of "scientific calculators", slide rules disappeared very quickly.
  Although they gave only 3+ digit accuracy, because we had to keep track of decimal point separately, and we had to be aware of the behavior of the formula, slide rules are very good tools for understanding the real world. Recently I started collecting slide rules. I started from scrach, because I no longer had the one I used to use long time ago.

Trivia: Most of the slide rules come in 4, 5, 10 inches. The length refers to the actual scale length, not overall length of the rule. Also, scale lengths are in metric. So, a "10 inch" rule has the scale length of 25.0cm exactly.

Please visit Slide Rule Annex for my complete SR collection and more detailed discussions on slide rules.

 Farber Castell's late model. This model is regarded as the ultimate slide rule and has most of the scales ever invented. This is "a big brother" to the 5-inch model 62/83N, which has the same set of scales as this model.
 It has impressive 30 scales.
Front: T1, T2, K, A, DF [CF, B, CIF, CI, C ] D, DI, S, ST, P
Back: LL03, LL02, LL01, LL00, W2 [W2', CI, L, C, W1'] W1, D(LL0), LL1, LL2, LL3

 A duplex for general use. Bamboo body with celluloid. ; Front scales are DF [CF, CIF, CI, C] D, L. Back scales are K, A [B, TI2, TI1, SI] D, DI. It has total of 15 scales. DF, CF scales are folded at srt(10), rather than pi. I bought this rule at a store in 2000.

  Designed for communications engineering, this rule has a special set of scales for calculating the resonant frequency of a coil and a capacitor. An ingenious system of keeping track of decimal positions is implemented.
 This is the model I used when I was a student. My current stock is a recent acquisition because I lost it a long time ago.
It has total of 19 scales.
Front: L, db, DF [CF, CIF, CI, C] D, LL3, LL2, LL1/ Back: A, L' [C', SI, TI] D, Lambda, F. Scales L' and C' in back are not the regular scales. They represent inductance and capacitance, respectively.

  A duplex for general use. Bamboo body with celluloid. Front scales are; LL/1, LL/2, LL/3, DF [CF, CIF, CI, C] D, LL3, LL2, LL1. Back scales are L, K, A [B, T, S, ST, C] D, DI, LL0, LL/0. It has total of 24 scales.

 Keuffer & Esser's early slide rule (1920s?). Made with mahogany body.
Scales are; front; A [B, CI, C] D, back [T, S, L]. Also, K scale is on the front sie. It has total of 9scales.

 Made with mahogany core with celluloid. For decorative purpose, only part of sides is covered with celluloid so that wood is visible at front and rear sides. I like the design.
Scales include; (Front) DF [CF, CIF, CI, C] D, L, (rear) K, A [B, T, SRT, S] D, DI. Total of 15scales.

 One of the Pickett's most sophisticated slide rules. This model is in whiTe.
Front scales include; Srt, Srt, K, A [B, ST, S, T, T, CI] D, DI, Cuberoot x3.
Back scales are; LL0+, LL0-, LL1+, LL1-, DF [CF, CIF, Ln, L, CI, C] D, LL2+, LL2-, LL3+, LL3-, P, S. This rule has Total of 32 scales.

 This bamboo rule out of Post is an OEM from Hemmi. Front scales include; LL0, LL/0, K, DF [CF, CIF, CI, C] D, R1, R2, L. Back scales are; LL/1, LL/2, LL/3, [T, T, SecT, ST, Cos, S, C] D, LL3, LL2, LL1.
Total of 26 scales.

 This bamboo rule has 25 scales. Front; LL1-, LL2-, LL3-, DF [CF, CIF, CI, C] D, LL3, LL2, LL1, and back; LL0-, L, K, A [B, S, ST, T, C] D, DI, P, LL0.