A frequency oscillator tuning process at the manufacturing stage is replaced with an adjustment of a resonant circuit in the frequency oscillator during an operation of the oscillator. According to one embodiment, an oil-based slurry with particles of a known size is applied to a lapping plate. The cover includes guide slots for slidably receiving side portions of the anchor and a ramped surface automatically moves the lid from the closed position to the fully open position in response to the housing moving relative to the anchor.