Actually, years later I did encounter what might be term as a non-imperial (though not metric) protractor. It was marked up in grads (400 grads = 360 degrees).
I've never found a good explaination of when or where grads are useful as opposed to degrees or radians. They do show up on all three of my scientific calculators and even in the calculator on Windows in scientific mode.
I just found this which appears blames the grad on the (former) British Imperial Army, so maybe they are imperial and degrees should rightly be called metric.
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