1932-1941 - Hemmi-manufactured rules have no date code and are marked "Made in Japan" 1941-1946 - WWII.Post buys slide rules from Lawrence Engineering Service, Charvoz-Roos, Bruning and Gilson.Post also sold branded slide rules from Richardson, Vicari, Boucher, Sexton, Halden, Chandler, Ritow and Winslow.

rules of dating in 1940-32

The Bruning boys work for another blueprint company. 1893 Frederick Post, Charles Bruning, and Jacobi form their own blueprint company in Chicago under the name Post, Jacobi, & Bruning. 1962-1975 -The numbers were converted to a 68-xxxx number series.

The downloadable charts are a matrix of Dietzgen slide rules, catalogs and price lists that was compliled by Bruce Babcock, Ph. and was published in the Journal of the Oughtred Society (JOS) October 1996, Volume 5, Number 2.

up to 1932 - Post slide rules were made by German manufacturers Dennert & Pape, Nestler and Faber.

1932 - Post began buying all of its straight slide rules from Hemmi Keisanjaku in Japan.

Dates that a design was registered or patented only suggests an approximate year a model may have been first produced, as the model may have been distributed a year or more before issuance (patent pending). There were three rollovers occurring in 1943-1944, 1954, and 1962.

The patent may only refer to a certain combination of scales used over a thirty year time on different models. 1911 James Dieterich, who has worked his way up to blueprint foreman at B. Makepeace Co., goes west and lands a job as a salesman with the K&E branch in San Francisco. In general the production rate was about 70,000 rules per year until the 1950s. The 1960s had a production rate of about 100,000 per year for several years and tapering off in the 1970s ending at about 700000.

Found on manuals and other slide rule ephemera: 1909 - Copyright Act on published works passed by Congress. 1951 - 3 digit Area Codes in Phone numbers implemented by AT&T (Developed in 1947). 1897 New York Blueprint Paper is founded by Charles Bruning in January. The common rules were produced in regular batches but the specialty rules did not sell as well and a given batch of rules might stretch over several years.

COPYRIGHT XXXX and © XXXX 1943 - 2 digit Postal Zone codes to increase efficiency of delivery because of a wartime shortage of staff. 1963 - The use of 5 digit Postal Zip Codes in USA addresses adopted but not mandantory. 1898 After a fire, Bruning rebuilds the New York Blueprint Paper Co., only to close it and return to Chicago. It is not uncommon to find rules in the 1960s in 68 xxxx series packaging but 4000 series model numbers on the rules.

The dash number scheme for length variations was abandoned.