I started as an Instrument Apprentice in 76 and found myself using both imperial for older kit and metric for any new kit purchased.
In those days Instrumentation was more pneumatic control in psi with new or foreign kit coming in barg.
Temperatures varied from Fahrenheit to Celsius to Kelvin
Pressures from psi to Barg to BarA (atmospheric)
Distance was a combination of imperial and metric
Weight was pounds / stones to Kg
Coming from an age where holidays abroad meant conversions to francs, drachma, Pesetas and eventually Euros. Happy days.
Dave