This probe was previously the property of the vibration analysis and reliability engineering lab at Storage Technology Corporation (STC / StorageTek / STK) in Louisville, Colorado. STC operated one of the most advanced mechanical‑systems and materials‑analysis groups of the 1980s–1990s, and many of their ultrasonic tools were OEM‑only builds sourced from Metrix.
This PT50212 is a Metrix OEM transducer. Units from this era were produced in small batches for industrial R&D labs and rarely appear on the secondary market in this condition.