Patent for manhole cover, 1895. A revision to an earlier design (see above), this manhole cover has a recessed section that is filled with asphalt or other paving material. Patented by Thomas P. Greger on April 2, 1895. U.S. Patent No. 536,621, pp. 1-4.

Source: United States Patent and Trademark Office at http://www.uspto.gov.