Grid Dipper

For a long time, the grid dip meter was the ‘HF multimeter’ of every RF engineer or technician. Like an ordinary multimeter, it is a simple instrument that can be used for a wide variety of quick and useful measurements on high frequency circuits, such as determining the resonant frequency of an LC circuit, determining the values of unmarked coils or capacitors, and checking the signal paths of RF stages. Here's one from the early 1950s.