There was a 5' rotary cutter listed in the ads of one of the local rags, so I went out to have a look at it. Turned out to be a JD 506. It was in pretty good shape, but not knowing much about rotary cutters, I wasn't sure about whether it was a medium or heavy duty model. I googled it when I got home, but did not find much info. Does anyone know anything about this model?