Engraving Plate for Library Company Letterhead. Biddle Press. Library Company of Philadelphia. Letterheads. Business -- Forms. Reads: “Library Co. of Philadelphia, Philadelphia.” The Library Company’s seal is at the left. Ca. 1939 Engraving plate. 3 1/2 x 5 5/8 x 1/8 inches. digitool:59450 OBJ 687 OBJ 687