The data covers all Teletrade, Heritage, Bowers & Merena, Superior and Stacks auctions since June 1996 for which prices realized is available to the compiler (i.e. a few auction sales for these firms aren't included: data is not complete).
Only the three most recent auction sales for each grade are included.
Some of the lots have been re-acquired by the consignor, especially for Stack's sales. Stack's does not distinguish buybacks in their prices realized, unlike the other firms.
Not all data has been double-checked (i.e. some database entries may be incorrect).