To follow up on my own post. If it's a model number
number it's probably 5s29, and is at the place pointed
to in my previous post. If it's a chassis
number 5529 the Zenith oracle says
that chassis 5529 was used in a handful
of 5s3xx series radios. The schematic is
Riders 9-11, Nostalgiaair has it at
http://www.nostalgiaair.org/Resources/008/M0025008.htm

Oz