Hey there!  You're looking at a Zenith Service Manual for models Z419, Z422, Z426, Z470, Z474, and Z476 FM-AM Transistor AC Radios.  In particular, this manual is for those using chassis BZT13, BZT14, BZT17 & BZT18.

If I am reading the code on the manual correctly, I believe this manual was printed in 1968.  It is a short manual, but this copy is in excellent condition.

Thank you for looking, and please let me know if you have any questions.