In 1888 Mr. Shallenberger was issued a patent for his invention from the United States Patent & Trademark Office (USPTO). There were 6 documents on file for this patent. The drawing specification sheet of the patent has been reproduced from original USPTO documents and printed onto parchment paper. This print is sized and ready to install into an 8" x 10" frame. The additional sheets included are printed on 5.50" x 8.50" parchment paper. These accompanying documents describe the scope of this invention in formal terms. The following is an actual excerpt from the patent…

       " Be it known that I, OLIVER B. SHALLENBERGER, a citizen of the United States, residing at Rochester, in the county of Beaver, in the State of Pennsylvania, have invented certain new and useful Improvements in the Method of Measuring Alternating Electric Currents, of which the following is a specification. The invention relates to the class of apparatus employed for measuring electric currents and recording the amount of electrical energy consumed in any given circuit or portion thereof"…