Robert,
Its an oak-faced 1/4" plywood sheet thats been kicking around here for the last 33 years. It was supposed to be used in a carpentry project that never happened. I'm using it temporarily as a tabletop to perform clearance tests and track layout measurement. The final tabletop will be 1/2" Baltic Birch plywood under homasote.
Back in the day when I bought it, it was $80.00. Seems like a pittance with today's prices. At some point it got wet, so now its just a work support.