The Olympus Evident A539S-SM Angle Beam Transducer is an ultrasonic transducer used for testing weld integrity. It has a frequency of 1.00 MHz and an element diameter of 0.50 in.
It comes in a miniature screw-in case style with a straight microdot connector. It is used with a wedge to introduce a refracted shear wave or longitudinal wave into a test piece. 
 
Olympus ultrasonic probes and transducers are used for flaw detection, thickness gauging and materials research.