I've never actually seen a "metric" ruler with non-decimal divisions, but that would work. People go the other way too--some American machinists work in 'mils'

I've never actually seen a "metric" ruler with non-decimal divisions, but that would work. People go the other way too--some American machinists work in 'mils' (=1/1000 of an inch), since one often wants (and can achieve) that kind of precision.