Jack,decent Series II D-21 AC's are going in the $6,000 price range these days.One needing some work is in the $3-4,000 range and a fully restored one is $10,000 or more.210's are priced about the same.
I recently sight unseen bought a 1965 Series II D-21 in Montana but dont have it home yet.Its a bareback,clutch slips a little,and one rear rim has a little calcium damage.You can see it at www.crankyfarmer.com Its the one going to MO.