Buffalo WYR-G54

User manual (via archive.org)

This device is a SerComm IP806SM.

"4900MZ20" is silkscreened on a production unit's board.
 * This particualar board is using Capacitor brand used::TEAPO and Capacitor brand used::Sanyo capacitors.

The manual states the default SSID is the device's MAC address.
 * Per an actual unit, this is indeed correct - it is the standard Buffalo default SSID format..
 * the MAC address of the device w/ no delimiters and upper case characters.