I looked all over for a date and got everything from “early 1800s” to “late 1800s” but nothing exact, so I had to make an educated guess. The first cameras practical enough to take such a photo were developed around 1840 and the excavations began in 1867.
I felt that copyrighting it in the year nothing might have been a typo.
Also, there’s absolutely no question that it’s public domain.