Canon AT 1 - Manual (Page 55)

Angle Finder A2 and B
The angle finder is a magnifying glass
which can be attached from above into the
grooves of the viewfinder eyepiece. It rotates
90 degrees so that the image on the viewfinder
can be viewed directly from the side or above
whenever it is inconvenient or impossible to
look directly through the eyepiece. This is
very helpful in copying, close-ups, macro­
photography, and photomicrography. There
are two types, the A2 whose image is reversed
as in a mirror, and the more advanced Angle
Finder B which gives a correct image.
Magnifier S
The Canon Magnifier S gives 2.5X magni­
fication of the viewfinder center for precision
focusing in close-up work. The strength can be
adjusted to your eyesight within the range of
-f4 to —4 diopters.
The Magnifier S combined with its
adapter can be inserted into the grooves of the
viewfinder eyepiece. The adapter of the
Magnifier S is hinged to allow the magnifier to
swing upward from the eyepiece leaving the
whole screen image visible after focusing.