|Manufacturer:||Albert Nestler Lahr i/B||Albert Nestler A.-G. Lahr i/B.|
|Length:||27,6 cm||29,5 cm|
|Material:||plastic on mahogani||plastic on mahogani|
|- Front:||cm, K, A [B, CI, C] D, L, 1:25|
|- Back:||[S, ST, T]|
|Case:||two part, black paper-case||missing|
|Cursor:||missing||glas with metal frame, with 4 hairlines|
|Extras:||no extras||no extras|
Here are two variants of the same slide rule. Because of the missing information it is difficult to determine the year of production, but the statemant "D.R.Patent" ("Deutsche Reich Patent"- German empire patent -therefor before 1945) on the body does an approsimately classification.
Both slide rules have among a centimeter-rule above the body a rule on a scale of 1:25. A unit has the length of 4 cm, which corrosponds to 1 m.
The probably older No. 23 is a bit shorter, and has no extensions of the scales. The design of the scales is a bit different, the numbers are all one-digit, which is quite rare on slide rules of this length. As a special feature has this one an additional centimeter-ruler (from ca. 29 cm to ca. 54 cm) under the slider. You can measure, with help of the slider, which has to be pulled out, those length. The left edge of the body is zero, the right edge of the slider is the measuring point. At the left edge of the slider can the length be seen on the body.
The Nestler No. 23R is a bit shorter, but has extensions of the scales. But the additional centimeter-rule under the slider is missing.
On the back of the slide rules is an overview over important constant and conversions. On the No. 23R is the overview readable, on the No. 23 it is well-thumbed.
Front, No. 23
Back, No. 23
Front, No. 23R
Back, No. 23R