The schematic might be found here in this list of A.K.'s http://www.nostalgiaair.org/Resources/042/T0000042.htm
It has 55, 55C,F,FC, Early and late models
http://www.atwaterkentradio.com/ak55_ib03.htm
:The following site has the Instructions for Atwater Kent Models 55 and 60 Receivers, and is probably what you are looking for. The pages can be printed out directly from the web site.
:
:http://www.atwaterkentradio.com/ak55_ib03.htm
: