Standard Azimuth Mark disks replaced azimuth Reference Marks about 1935. This Ebright Azimuth is from 1933 so is a Reference Mark with the work Azimuth field stamp on it.
This photo was screen shot from a link on https://www.geocaching.com/mark/details.aspx?PID=JU3626 . See orignal at https://s3.amazonaws.com/gs-geo-images/9e9199b9-daa3-49f8-a1c0-a1547e7a73ac.jpeg
This image is attached to the The exact highest natural point of Delaware was never located while it was natural, and now is lost forever.