WWVB NIST Radio Time Receiver Kit - WRL-10060 - SparkFun Electronics
A New Architecture for Miniaturization of Atomic Clocks Exploiting a Piezoelectric-Thin-Film Vibration From a rack-mount system toward a microchip | Tokyo Tech News | Tokyo Institute of Technology
Space Chip Scale Atomic Clock (CSAC) | Microsemi
I designed an Atomic clock arduino shield! BOM cost is a cool $9000 : r/electronics