The JD 820 was a lot better than a JD 1219 or JD 1209. They just got them to the market too late. The disk mowers had already taken the market over. Plus the JD 820 was about $1000 more than the NH 492. So JD did not sell many of the JD 820s.
The rolls are place lower on the JD 820 and that made a big difference in how the hay feed through them. Plus they had a much heavier tongue system on them.