SR-Annex : Collection: Notes

Notes about scale description, etc.
Image sizes Throughout "Slide Rule Annex", images are shown in either 60 dot-per-inch (DPI) or 120 DPI to preserve relative sizes of the slide rules consistent. For 10 and 20 inch rules, 60 DPI is used to show the whole rule, and 120 DIP format is used to show scale details. For 4 and 5 inch rules, whole rule is shown in 120 DPI and no separate details will be shown.

Scale Description Scale Description Method which is used by Herman van Herwijinen is used here.
For example; if you see "10cm/ K, A =B, CI, C= D, L | 4in", it means that;

1. Top side of stator is slanted and there is 10cm of linear scale.
2. Upper part of stator has K and A scales, B, CI, and C scales are on
  slider, D and L scales are on bottom half of stator.
3. Bottom of stator has 4 inch of linear scale.

Which side is the Front? Front side of a simplex slide rule is obvious. But it is not obvious for duplex rules. Herman van Herwijinen's definition is that (1) the side which has A, B, C and D scales (2)or, failing that, the side with DF, CF, C and D, is the front.
For unequal stator length rules, such as Hemmi 255D or K&E 4081-3, if you hold the rule with longer stator at lower position, this gives generally acceptable "front side".

I am proposing here that, for the duplex rules, the front side is the side on which the head of the adjusting screw is. This is based on my assumption that the designer must have had his/her idea of "the front side" and must have placed the screw head on "the front side". Defining screw head to be "front" is, therefore, is to try to follow the manufacturer's idea of which side is the front side of that particular slide rule.

Having said that, I may stray from my own dictum. As the saying goes, there is no rules without exception! (pun intended ; - )

Code on Note *1 = with magnifying cursor
*2 = Donald Murtagh Collection: These rules came from his collection.
Other = Date code, etc.