Monroe model K-120 calculating machine, manufactured in 1922 in Orange, New Jersey. Image courtesy of the University of Michigan Museum of Anthropological Archaeology. Photo by Jim Moss.

This strange-looking machine, with its parallel rows of numbered buttons, was "discovered" in plain sight this summer on top of a cabinet in the Coffee Range. It's a mechanical calculator, and legend has it that at least one famous U-M archaeologist used it back in the day. The Monroe Calculating Machine can perform the four basic rules of arithmetic—addition, subtraction, multiplication, and division—using only gears and rotors. While not officially part of the UMMAA’s collections, which are archaeological and ethnographic in nature, this particular machine was important to the development of scientific archaeology. In many museums, if an object survives long enough, it too becomes part of the collection.

The Monroe Calculating Machine Company was founded by Jay Monroe in 1912 in New Jersey, based on the patents and designs of Frank Stephen Baldwin. This machine is the model K-120, referring to the 12 number places to which the machine can calculate. The company also made 16- and 20-place models. Production of the model K began in 1921, which makes the Museum’s machine more than 90 years old.

According to Jeff Parsons, emeritus curator of Latin American Archaeology at the UMMAA, this machine was used by Albert Spaulding, the Museum’s curator of archaeology from 1947 to 1958. Spaulding used the machine while developing his statistical methodology in anthropological archaeology.

Spaulding is probably best known to archaeology students as one half of the Ford-Spaulding Debate. The title of his 1953 article, "Statistical Techniques for the Discovery of Artifact Types," aptly describes his focus. He argued for the use of statistics (a new concept in archaeology at the time) to demonstrate that a combination of attributes can be considered an artifact type. For example, in a sample of pottery vessels, do material (e.g. grit temper) and design (e.g. stamped surface) coincide in a way that can be defined as an artifact type?

Spaulding was well aware that these attribute combinations must still be explained and he concluded with an “often repeated warning that statistics are never a substitute for thinking. But statistical analysis does present data which are well worth thinking about.”

Spaulding was a strong advocate for developing methodologies that would make archaeology more scientific. When he left Michigan, he became director of the newly created anthropology program at the National Science Foundation, where he was able to shape the program and encourage the NSF to take archaeology seriously as a science.

Gordon R. Willey, a classmate of Spaulding’s at Columbia University, remembered him this way: “His manner of speaking was very precise, almost exaggeratedly so. He did this to make his points, and his points always added up to the proposition that archaeology—if not yet a science—should be one, and that the best way to bring this about was for its practitioners to be certain of what they were saying, to be specific and, if at all possible, to be quantitative.”

Obviously, having a good calculator would be helpful.

See the machine in action here.

For further reading:

Chase, George C. “History of Mechanical Computing Machinery.” Annals of the History of Computing 2, no. 3 (1980): 198–226.

Ford, James A. "Comment on A. C. Spaulding, "Statistical Techniques for the Discovery of Artifact Types." "American Antiquity 19, no. 4 (1954): 390–391.

Spaulding, Albert C. "Statistical Techniques for the Discovery of Artifact Types." American Antiquity 18, no. 4 (1953): 305–313.

Spaulding, Albert C. "Reply to Ford." American Antiquity 19, no. 4 (1954): 391–393.

Voorhies, Barbara. "Obituary: Albert C. Spaulding, 1914–1990." American Antiquity 57, no. 2 (1992): 197–201.






Monroe advertisement for the Model K-120, circa 1922 (Rechnerlexikon: The great Encyclopedia of mechanical computing. Accessed July 30, 2018).

Parts diagram from a 1919 Instruction Book for the Model G (Monroe Calculating Machine Company 1919).

Edward Scully (left) and Albert Spaulding (right) preparing to leave for southeastern Missouri in 1952. (U-M Library Digital Collections. U-M Museum of Anthropological Archaeology. Accessed: July 30, 2018.)