  A seller chooses a reserve price in a second-price auction to maximize
worst-case expected revenue when she knows only the mean of value distribution
and an upper bound on either values themselves or variance. Values are private
and iid. Using an indirect technique, we prove that it is always optimal to set
the reserve price to the seller's own valuation. However, the maxmin reserve
price may not be unique. If the number of bidders is sufficiently high, all
prices below the seller's valuation, including zero, are also optimal. A
second-price auction with the reserve equal to seller's value (or zero) is an
asymptotically optimal mechanism (among all ex post individually rational
mechanisms) as the number of bidders grows without bound.
