I could not find any pics of the internals of these watches, so pic here

http://diverse.4mg.com/casio_wr50m_r.jpg

The wire to the antenna broke , handling the pcb for this pic and
self-weight of the small coil, not before, but it is obviously a week
point at the solder points if subjected to a lot of vibration.
For the moment I'll clean battery and contacts and reaasemble to check
that I can and run for a while, until date 2005 returns presumably, and
hopefully find out more info on the internals.
The yellow caret marks a SMD with 200mV on it 20 minutes after removing
the button cell, 3.06V open cct voltage.
Seems 3 crystals relate to the radio blob and 1 for the watch. Red is my
mark for +ve so I can solder a pair of wires to convenient spot , to
power from 3V to monitor some DC levels at least, next time of playing
with it that is.
Beware of the tiny phosphor-bronze spring dropping out, on disassembly
of the 2-part plastic sub-frame, it connects to the piezo sounder.
Battery contact simply slides to release battery. A number of tangs need
prizing back with a needle to release the metal screen and 4 spring
tangs for the button returns.