This catalogue is interesting as it gives details
for items from *three* ranges:
  The 425 FM receiver and 426 FM/AM receiver.
  The 521 amplifier, 523 AM/FM tuner, and 524 FM tuner.
  The 127 AM/FM receiver.
  Stereo docoders M4 and M5.
  (M8 decoder not mentioned.)

Also an interesting misprint on page 1
(inner front cover) which refers to a '623'
when meaning a 523.