This is a vintage Mitten's Movie Titler PLT-1.  It seems to have never been used.  There are 153 letters/symbols that are 3/4".

Box has been taped at the corners.

Mitten's Movie Titlers were popular analog filmmaking kits prodsuced by Mitten's Display Letters (originally based in Redlands, California).  They allowed amateur and professional filmmakers to creat tangible three dimensional title cards for movies and home videos by arranging individual pin backed letters on specialized display board.

Please email me with any questions and thanks for looking.