IMPERVO

OUTDOOR ADVERTISING DISPLAY SIGNS MADE OF AN INTERMEDIATE CARDBOARD SHEET IMPREGNATED WITH A WATER-PROOFING MATERIAL HAVING BONDED THERETO A PAPER BACKING SHEET AND A PRINTED OR LITHOGRAPHED PAPER FACING SHEET, SAID BACKING AND FACING SHEETS HAVING BEEN MACHINE SURFACED WITH A WATERPROOFING COMPOSITION PRIOR TO BONDING TO THE INTERMEDIATE CARDBOARD SHEET, THE EDGES OF THE COMPOSITE STRUCTURE HAVING ADDED WATERPROOFING MATERIAL APPLIED THERETO