I’ve been looking for a metal type scale – I did have one when I was a student at Liverpool Polytechnic but I’ve mislaid it, probably thinking “I won’t be needing that again!”
I found one in the US on ebay.com – with both picas and agate measurements on – it’s a useful 24 inches long with a handy hole to hang up.
I’ve never heard of an Agate so I’ve discovered it’s a measurement relating to 5.5 points, or about 1/14 of an inch. An Agate font is commonly used to display statistical data or legal notices in newspapers. It is the smallest point size that can be printed on newsprint and remain legible. The Guardian has a specially designed Agate sans for use in it’s classified and sports sections.