619
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.
A not very trustworthy looking hungarian website says 1890
https://pressnavigator.hu/photold/2023/03/25/photo-of-the-great-sphinx-from-a-hot-air-balloon-this-is-before-it-was-excavated-and-restored-1890/
Maybe, between two excavations, the wind has partly filled up the cavity of the previous excavation with sand and thus, the progress wasn't continuous.
This is supposedly from 1867 - 1878:
Wikimedia Commons