The image above can be seen in much better resolution here, a page of the National Museum of American History, Kenneth E. Behring Center (via DPLA and Smithsonian Institution). It is a late-1800s colorimeter, not produced by Joseph Lovibond, the English originator of the colour slide system to measure colour in malt and beer, but something similar used in an American brewery. An extract from the narrative on the page:
This colorimeter is part of a large collection of brewing material donated to the museum in 1967 by former brewmaster Walter Voigt, of Ruxton, Maryland, near Baltimore. Voigt’s collection consists of objects and archival materials reflecting the history of brewing in the mid-Atlantic region between 1870 and the beginnings of consolidation and large-scale, industrial production in the 1960s. His correspondence reveals an interest in preserving the history of brewing in America before brewmasters were “replaced by chemical engineers and highly trained chemists in modern laboratories.” Voigt’s papers are housed in the museum’s Archives Center, Collection #ACNMAH 1195, “Walter H. Voigt Brewing Industry Collection, 1935-1967.
It appears the instrument was used in a pre-Prohibition brewery in Baltimore and possibly after Repeal as well.
While time has dimmed many of the slides and also the light doesn’t penetrate each in the same way*, the amber slide on the left-centre (opposite the white oblong) has a remarkable clarity. This is no. 13 of 16 slides counting from the top-centre clockwise.
In A.L. Nugey’s 1937 Brewhouse Formulas Practically Considered, which I have referred to numerous times on the blog, he states as a rule of thumb that anything over 12 degrees L. can be considered dark, anything under 12 pale or light, but also that both pilsenser style and Dortmund beer top out at 8 degrees L.
Given Nugey was writing just a few years after Repeal, there is every reason to think his comments represented a pre-Prohibition norm. (Other data in the book show similar reliance on the older industry, in particular finishing gravities and hopping rates).
Look at no. 13 slide again from the link given (i.e., best resolution) and consider what nos. 12, 11, 10 would have been like: marginally lighter on a decreasing scale. When you compare these to the various images I have posted of 19th century lagers, one can see that the pre-Pro norm for the older form of lager, the reddish-brown I have discussed, was 9-12, while the newer pale Bohemian style was probably 6-8 L.
Anchor Steam beer, and Sam Adams Boston Lager which is a recreation of an early American lager, give some idea of what the older lager was like, indeed in taste as well as colour.
In the post-war era, Nugey’s no. 8 if not often lighter became much more characteristic of American beer.
Today, the SRM system is used in North America to measure colour, but it operates to a similar principle (multiply L. by 1.3 to get a working equivalent in SRM). The Europeans have another nomenclature and scale, but again similar in principle. A Lovibond scale is still used to denote colour in the malting industry.
*I’m thinking now the metal “tray” is a handle that rotates the disk and opens the window to illuminate the slide needed. If so, it’s remarkable that it is fixed to no. 13 which I posit as “the” color of 19th century standard American lager.