The 1970's BOSCH hand held Strobscopic Timing Light with adjustable timing angle was a must for every professional motor mechanic or even the well equipped hobby mechanic.
A must for any engine tuning.
The pocket hand held tester was a must for any mechanic in the day, with a RPM meter, Dwell angle, Volt meter, Ohm meter for 4, 6 and 8 cylinder cars.
What more would a mechanic need.
