Not a miller. The first tip is that this photograph came from the upstate New York State area. As a native New Yorker from Queens, anything north of New York City is Upstate. This photograph is from upstate in the far western regions just bordering Pennsylvania which include the city of Corning. Ring a bell?
Sure enough, the worker is a glass polisher, hard at work at a belt powered polishing machine. It looks as if there is a water spout above, feeding water though a narrow trough to a thin polishing wheel. Glass dust is caught in the bin underneath the polishing wheel.
Behind the worker you can see a line up of a variety of pieces either finished or waiting to be polished. I have a feeling he is polishing the bottom of finished pieces before they are sent out for sale.
The polishing apparatus is fairly rough overall, having only a spindle mounted in wood uprights and lacking any discernable babbit bearings or other metal bearings. A light touch must have been the order of the day.
Sadly, there is no annotation on the front or the back of the photograph.
Till next, Gary