calculating ruler??

[Bowfrog]

Here is a pic of a ruler that comes as a pair. No idea as to what it was used for... Anyone have any thoughts?


Thanks for your help!

 

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[mcl]

It's a ruler with different divisions of inches or centimeters. For olden days engineering/design when you measured things to tolerances, e.g., 15ths of an inch. Google "engine divided".

They had different purposes, e.g, back in the days when computers were programmed with punch cards, they had divided rulers that had card numbers marked so you could see if you had a stack of e.g., 250 cards, without counting them.