1. This rule could be considered part of the 2/8* family of Faber Castell duplex slide rules, the other ones in my collection being the 2/83N and the 52/82. The rules however have significant differences of scales.
2. The rule has 24 scales, more than than the 52/82 but less than the 2/83N.
3. Although produced around the same time as the other two rules, this one shows no sign of the ink bleeding. On the other hand one face has yellowed by light.
4. This rule has metal end braces which are covered by a short rubber sleeve -shown on one of the detail pictures below.
5. One unusual feature of this rule is the inclusion of two K (cube) scales, one on the stock and one on the slide. The only other rule I have with these scales is the Pickett Texas Speed rule which was targeted at the annual slide rule competitions in that State which included a lot of work with cubes and cube roots. Could this have been Faber's attempt to get some competitive advantage in the US market?
6. I also show and earlier variant of this rule - made in 1957, ten years before the main rule. The early variant showed a number of anomalies, for example having some trig scales (T1, T2 and S) on the stock and some (ST) on the slide.