As the Conté process of making pencil lead from a composite of ceramic and graphite was adopted industry wide in the 1850s, it became possible to produce leads with a consistent variation in hardness and darkness. Early attempts to create a standard for identifying the varying degrees (as we now say) differed between manufacturers.
A.W. Faber Artist's Pencil (circa 1890). The lead degree indication consists of a repetition of six H's.
Alteneder Draftsman's and Artist's Pencil (circa 1930).
The Alteneder Draftsman's and Artist's Pencil is the first instance known to me of a modular indicating system for lead degrees. The high price of this well made pencil drove the development of a more efficient method of indication than entire pencils marked with degrees. The solution was a set of interchangeable chuck clamping sleeves, each with a single lead degree designation. Although an improvement over entire pencils differing only in the degree markings, this method was not ideal. The tiny sleeves were easy to misplace and unless you bought the entire range of them, you might not have the particular one that was needed when circumstances required it. Perhaps the most important deficiency was the close inspection required to identify the markings on the clamping sleeves.
An early A.W. Faber Castell Locktite (circa 1950). By this time the number/letter system had been adopted, but leadholders were still made uniquely marked for each grade.
This pencil is from the 1990s and still has an inefficient specific degree imprint.
The following five leadholders each have a variation of a removable indicator that can be positioned to highlight a specific lead degree designation.
This group of seven leadholders illustrates the spectrum of different rotating indicators.
A sliding indicator.
The unique Staedtler colored pushbutton system of identification. Each pack of lead includes a plastic pushbutton that fits Staedtler leadholders.
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