I have worked with drawings done by many people. I can always tell the designers with metric brains from the inch brains, when looking at their drawings, no matter what units are actually on their drawings. People with inch brains are used to using fractions of an inch, and you should normally see "3.375" to represent 3+3/8". But the metric brains will produce drawings with 3.386" dimensions, and they will think it makes sense when it doesn't. OTOH sometimes I get a metric drawing where inch-brain designers will produce crap like 304.8mm because they actually designed the part in inches and slapped metric dimensions on, letting CAD take care of the conversion.
Jimmy Carter is my hero.