Bart i have no idea of how to check oil pressure of the internal system.
teh difference between cable and electronic hours:
the electronic clock is like a stopwatch, counting how many hours the engine has been running.
The cable clock measures how many revolutions the engine has made. Ferguson 35 clocks measured one hour at 1500 rpm, so if you run it for one hour at 1500 rpm it says 1 operation hour, one hour at 2000 rpm makes it 1.33 hour.