I found it several places on the Internet. One place the caption was:
Paul Maciulaitis image title is Woman at BASF gas engine power house in 1917
[The comments point out that it looks like the alternator is turning fast because of a slow shutter speed. The woman is holding a pose while the picture is being taken. The wheel of that size is probably turning at 60-80 rpm.
An example of a large, slingle-crank gas engine.]
Here is a video of a restoration of such an engine being started up, running, and shutting down:
This thing is a real monster! :-o