Ian, what is in Focal Encyclopedia of Photography ?
I found a few from 1980, 1965 and 1969.
There's been various versions. I have a very large single book version from the 1960's, it was split into two in alter editions and there was also an abridged desktop edition and a smaller Pictorial Enclyclopedia of Photography.
They are all excellent, the two book version contains more detail particularly with regard to applied photography (outside normal uses). Even the desktop version is wort getting as it's still packed with plenty of information. I have 3 the Pictorial, Desktop and full their in storage so I'm not sure what dates.
The contributors were the worlds leading experts of their day. For analog use the older version are the best. Any 60's -80's will be OK but 1980 would be more up to date for colour work.