The module providing the GPS signal processing on this device is a µ-blox GPS-MS1 that's sort of ancient in the realm of modern electronics.

It was released June 29, 1999!

It features an astonishing 0.125 MB of SRAM and 1 MB of flash memory.

The backup battery on its reverse side powers a real time clock and maintains the GPS receiver's SRAM to allow for a much faster connection time to the satellites, called a warm start. This is usually used in conjunction with a circuit to power down most of the GPS, providing a much longer battery life.