Original electrical trade vintage catalog for PORTLAND-MONSON SLATE COMPANY, of Portland, ME. Manufacturers of electrical enclosures and panels. Typical switchboard panel installation is shown. Strongly preferred by well informed builders and buyers of electrical apparatus alike. Panels supplied to specified sizes, drilled to your template, ready for mounting. Disbound from a large 1949 electrical construction materials book, this unique old one page technical brochure would display wonderfully matted and framed. A marvelous addition to your retro electric equipment library.