One of the keys of the success of the Ford Motor Company and an enabler of Ford's mass production methods was the development and use of the Johansson gage blocks.
The method of manufacture of the gage blocks was developed by Carl E. Johansson. Ford was able to get the rights to the blocks and further development by purchasing the patents and putting the inventor on the Engineering staff of the Ford Motor Company.
These blocks were used on the shop floor to set up critical manufacturing operations, to calibrate measurement tools and gages, and to check parts production.
This capability was a key component of the standardization and production of close tolerance interchangeable parts which enabled development of Ford's mass production techniques and moving assembly line.
Close up of an individual gage block.
This is the standard 81 piece set of gage blocks.
There were also smaller sets available, including a basic five piece set consisting of 0.0625, 0.125, 0.250, 0.500, and 1.000 inches.
This set is housed in a bakelite plastic case and dates from the mid 1930's. Earlier Model T and Model A era sets were in fitted wooden cases.