We used one of these on the farm in the 1930s. It is a windrow attachment and is attached to the sickle bar of a mower. We always called them "pea rollers." I assume they were designed to windrow peas when cut with a mower. We used them when cutting alfalfa or clover for seed. They would gently roll the foliage into a windrow, thus saving seed as compared to using a side rake.
- Bob Schink via e-mail