Tachistoscope

Claim 1

A tachistoscope comprising, in combination: a hollow sleeve formed from a foldable blank, which blank includes; a front wall portion containing a viewing window, a back wall portion containing an index window, a first side wall portion disposed between said front and back wall portions and being defined by a first pair of parallel fold lines, a glue flap, and a second side wall being defined by a second pair of parallel fold lines which are parallel to the first pair of fold lines, wherein the viewing window and the index window are positioned in the respective front and back wall portions of the blank such that they are in alignment with one another when the blank is folded to form the sleeve; an index card retainable against the back wall to cover the index window and including information which is to be exposed to view through the viewing window; and a shutter adapted to slide within the sleeve from a first position in which the shutter blocks the index card from view through the viewing window to a second position in which it also blocks the index card from view, which shutter contains an opening oriented to align between the index and viewing windows at a shutter position intermediate the first and second positions, wherein the shutter is inserted into the sleeve by the user and released to fall from the first to the second position such that a person looking through the viewing window can momentarily see the information contained on the index card when the opening in the shutter passes between the viewing and index windows.