How about the obscure French system where they divided a right angle by 100 and called them grades. 400 grades to a circle. Incidently this why we measure temperature in Celcius not centigrade anymore.
Technically 'centigrade' is a generic term for a temperature scale with one hundred degrees in the interval between the freezing and boiling points of water. Celsius is a particular centigrade scale in which the freezing point is zero degrees.
So we are still using a centigrade scale, but called correctly Celsius.
Not many years ago, probably still some on the road, there were coaches with metric (nut and bolts) body, AF chassis and Whitworth engine! Good old Leyland!
I was in France last weekend and really surprised to pick up a ball joint marked 3/4". How come the continent accepted imperial pipe sizes and threads?