Vintage Wooden Slide Ruler Interlox No 106 Master Rule Mfg Co NY

Master Rule Mfg. Co. dates from 1919 when the company was located at 841 E. 136th St., which is only a few doors east of the sign above at 815 E. 136th St. It also indicates Master Rule's origins in the earlier Dahl Mfg. Co. In 1907 the inventor, Albert Dahl, secured US patent 870,940 for a Folding Step Ladder. His application began, "Be it known that I, ALBERT DAHL, a subject of the Czar of Russia, and a resident of the city of New York, borough of Manhattan, in the county and State of New York, have invented a new and Improved Folding Step-Ladder, of which the following is a full, clear, and exact description. The object of the invention is to provide a new and improved folding step ladder, for use by painters, interior decorators and other persons, and capable of being folded into a comparatively small package to be conveniently carried from one place to another, and also of being readily extended for its legitimate use More info at

• https://www.waltergrutchfield.net/masterrule.htm
• https://swingleydev.com/ot/get/246103/thread/
• https://mycompanies.fandom.com/wiki/Master_Rule_Manufacturing_Company
• https://archive.org/details/master-rule-hdwe-age-vol-168-no-2-1951-07-26-pg-98