It is a plywood product, with a paper face overlaid on the plywood substrate with an exterior grade (usually) phenolic adhesive. MDO is designed to have a smooth paint receptive surface. One or both faces can be faced with paper, and is found in 4' x 8' sheets from 3/8" to over an inch in thickness. MDO is used for short term signs. MDO is not recommended for permanent sign faces because it is susceptible to Warping, Water log, Mold Etc.
United Kingdom Intellectual Property Office Publishes Application for the Trademark "HI-FLOW" to Richmond Plywood for Multiple Product
Apr 21, 2010; SOUTH WALES, United Kingdom, April 21 -- Richmond Plywood Corp. Ltd., British Columbia, Canada, has filed the trademark "HI-FLOW"...