This is a great experimenters chip. Very easy to use and build into a circuit with minimal extra components needed to have a stable PLL up and running.. You will recieve one full unopened rail of 25 chips. NOS (new old stock) date codes '83.  The XR-215CN is a highly versatile monolithic phase-locked loop (PLL) system designed for a wide variety of applications in both analog and digital communications systems. It can operate on supply voltages from 5 volts to 26 volts and a wide frequency band of .5 Hz to 35 Mhz.