This is a vintage Sanford Vis-à-Vis overhead projector marker pen box.

Design Purpose: These pens are specially formulated to write on acetate transparencies for overhead projection.

Ink Type: They use a water-based, wet-erase formula, meaning markings can be easily removed with a damp cloth or tissue.

Features: The box highlights that the ink is odorless, quick-drying, and designed not to fade or bubble under the heat of a projector lamp.