The General Radio Experimenter

The primary article details early designs and advancements in using long, thin quartz bars to operate at low-frequency vibration modes (of the order of 30 to 100 kc).

It notes:Early bars were cut so that their faces were parallel to the principal axes of the quartz crystal (X-cut).Later developments showed rotating the bar about the X-axis improved performance characteristics.Figure 1 at the bottom provides a view of a Type 1190 Quartz Bar with its cover removed, demonstrating how the bar is suspended in nylon filaments held in tension by coiled springs to reduce mechanical shock and displacement.