Pan Am Boeing  727 Avionics Maintenance Training Manual.

I am guessing from late 1979 early 1980s as there is a real cool page(pictured in listing) With all the ex-National 727s,

there MFG#, Tail# and Model# with engine types.

  At bottom are 3 727s National acquired from Northwest in mid1979, so hence my guess on date.

2nd pic is table of contents, again all avionics, so its all Cockpit, sensors, Electrical lay outs schematics and graphs etc.

Manual is a shade under 1" thick(thick, but no indication on how many pages.)

Only 1 I have, and incredibly rare obviously. Good luck!