Old Tube Map
 

Lost the front (it was well-thumbed), but its defintely pre-decimal A-Z, 2/6
according to the list of prices at the rear. From responses so far (for which
I'm grateful), I think late 1950s.
BTW I forgot to mention in my original message the line stretching north from
Epping, not a through line apparently, but going via North Weald and Blake hall
to Ongar.