Panel 15

Panel 15 was a product that was made as part of Weyerhaeuser's Architectural Panels Division. In 1992 that division of the company became a separate company called Citadel Architectural Products (who still makes Panel 15 as one of their products). For any information on that product, contact Citadel. Their website is: 
http://www.citadelap.com/company/

Citadel Phone Number: 1-800-446-8828.