These Keystone Stereoscopic cards were meant to work with a special viewer. This company seems to have photographed the usual, landmarks and scenic vistas and included some work of the day, like this, with detailed, yet plainly written explanations on back:

"Linen is a cloth made from the fiber of flax. When flax is used for its fiber it is cut before it is ripe. The flax is pulled and the seeds are pulled off. The bundles laid in piles and rotted until the woody portion has decayed. The freed fibers are then shipped to spinning or weaving mills like in the picture. The first step is to heckle the fiber, combing the long fibers from the short. Then the fibers are sorted and coiled into bundles known as slivers. After the fibers have been drawn to proper length they are place in the roving machines here shown. You see the hanks of roving hanging on the right. The woman on the left is placing one of the hanks in the mill on a spindle. From the spindle the thread is wound on the bobbins. You see thousands of bobbins on tops of the machine. The white ones are full of thread, the black empty".