A batch code is printed or stamped on the bottom of a product packaging.Dating a slide rule becomes difficult if a manufacturer did not imprinting a date code or serial number on the stock. This comprehensive research will enable you to find the period of manufacture for most every Dietzgen slide rule from 1887 through 1972.Fred Post goes to work at Eugene Dietzgen's company. Removal of the "N" prefix also indicated a variation in the model.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.At one time or another Post brand slide rules were made by Dennert & Pape, Nestler, Faber, Hemmi, Lawrence Engineering Service, Charvoz-Roos, Bruning and Gilson.
1963 - The change from state abbreviations to two letter codes (Colo. to IL) 1967 - The use of 5 digit Postal Zip Codes in USA addresses now mandantory. 1896 Charles Bruning leaves Post & Jacobi, and after a honeymoon in Europe, returns to the US and settles in NYC. He sells his blueprint business interests to George W. 1899 In April, Charles Bruning returns to NY and starts the Charles Bruning Co. The Fuller and Thacher's slide rules had their own serial number systems. There were logical groupings of numbers and dash numbers were used to depict length variations of a given rule type.There are numerous examples of 68 xxxx series numbers on retail boxes and the slide rule inside has the old 4000 series number on it.We are sure that this was in the early 1960s while they were working through old 4000 series stock.Post buys slide rules from Lawrence Engineering Service, Charvoz-Roos, Bruning and Gilson.All Post slide rules with "Made in USA" come from this period.A batch code is an identification code assigned to a batch of cosmetics.It may contain information such as manufacturers code, production date, etc.It’s been said that Mars was likely once covered in a massive ocean, spanning almost half of the red planet’s northern hemisphere – now, UFO hunter claims he’s found proof. This also explains the three different boats we have found last year.‘I do feel Nasa went overboard with their 2 billion dollar fishing equipment to catch this one, but its defiantly worth mounting on the wall. Lets see how Nasa gets off the hook with this one, shall we?Among the rocks on the Martian surface, the alien enthusiast has spotted what he says is a large petrified fish‘I colored the fish to make it easier on the eyes. 1932 - Post began buying all of its straight slide rules from Hemmi Keisanjaku in Japan.1932-1941 - Hemmi-manufactured rules have no date code and are marked "Made in Japan" 1941-1946 - WWII.